It sounds smart but being new to timeshares I have no idea what you mean by these abbreviations
Ok, so MFs/pt is maintenance fees (yearly fee but not including club dues or booking fees) per point. In a system like HGVC you get points for your owned week. These points can then be used to book anywhere in their system. Points costs to book are fixed when a resort is built or acquired, but vary based on age (each time they bring on a new resort they tend to have more points required for the same thing - so older resorts were fixed when costs were cheaper), size of unit, view category and season. The seasons were also fixed when the resort was added. What this means is that at an early Hawaii resort and many of the existing resorts, a 2BR (2 bedroom) in platinum season (highest demand) is 11,200 points. However, a brand new Hawaii resort could be 28,000pts. A Myrtle Beach resort basic 2BR could be 11,200 pts platinum, but ocean front view would be 15,400 IIRC. On the flip side, that same ocean front view in gold season (so often called shoulder, or like for Myrtle Beach say April) is 9,650pts. Low Season, like Feb in Hilton Head might be 5,600 pts.
Now, you see how when and where you go can affect the points you need, the other side of it is that getting 11,200pts a year in Hawaii directly could be $3,000. In Orlando, it could be $1,800. In Las Vegas it can be $1,200. But the points spend the same. So you see the strategy. Buy where the MF is lowest for the points but adjust based on availability and up front cost. What is ~$4,000 up front in Orlando might be $8,000 up front in Vegas and a struggle to find one for sale because everyone wants the low ongoing fees for the points.
The other wrinkle is MFs are based on unit size, not season. So you'll find someone giving away for free up front an Orlando gold 2BR deed because it only gives you 8,000pts for the same $1,800 a year.
I am not intimately familiar with Marriott, but there are differences there. In resale Marriott doesn't give you points, you just get a week by default. To get points you also need to pay Marriott a junk fee of $3 per point. There is a lot of debate on TUG about whether this conversion is at all worth it - getting points means you can book less than a full week, but also means a different inventory pool than weeks, and often times I see reported the points values you get for a week are less than it costs to book it - which doesn't make a lot of sense to me, but I might be misunderstanding those posts too. If you don't pay for points, the weeks are traded in Interval International on a one to one basis, a week for a week. There may be a fee. The upshot of Interval trades is you can trade into more than just Marriott - if they're available and Interval thinks it's a like for like trade.
What Interval thinks is a like for like trade is a little opaque intentionally. From TUG I gather that there are a couple strategies, one is finding a low MF 2BR lock off, where you can split it into a Studio and a 1BR unit, so now you actually get 2 weeks to trade, though there's less trade power for a Studio and a 1BR vs a 2BR, Marriott gets such large trade power generally that you can often still find things, even 2BRs, and then pay the unit size upgrade fee to get 2 trades for one MF. The other strategy is to take a little foreign exchange risk and try and buy like Phuket Beach Club in Thailand which has worked out to a pretty low $1,200 MFs when converted for a 2BR. But of course the exchange rates change daily.
OK, so that's the basic strategic ideas - why would you willingly pay higher MFs per point or unit in a specific location? Well, to get much closer to (or actually) guarantee a booking each year where you want to go. When you're doing the strategy, you're betting that you can get online early enough of the inventory opening up during all access booking to get what you need.
If you own specifically where and when you want to go, you get an earlier crack at it. With HGVC everyone can book at 9 months out. If your actual owned week, called a home week, is what you want to book, you can book that with no booking fee at a year out - before anyone else who doesn't actually own that week, unit type and location CAN book it. It does cost all your points for that week however. This works like a traditional fixed week fixed location timeshare in that case. So if you need IDK July in Hilton Head or Christmas Week somewhere (these are usually event weeks that you have to buy specifically) then you're stuck paying more to lock that in. You might also have to spend a lot more for the week up front depending on who's even selling them.
Marriott I think if you buy a deeded week is fixed week fixed unit unless you pay for the points initially, or you deposit it into Interval to trade somewhere else, so in that case it's simpler, I don't think you have to go in and say I want to use it where and when I own, it does that by default, and you have to go do something if you DON'T want to use it that way.
Now, the other thing is you have to look at occupancy rates, HGVC 2BR are pretty much all 6 people max. So as I said originally, you're probably looking at trying to get 2 2BR in that system and trying to book them together so you have enough space. Here's where you kinda have to research if 3BR are even offered or if the 2BRs allow 8 people - some do, but not in HGVC and IDK about Marriott. If you're going to be doing multiple units, then you almost NEED the owned fixed weeks or to be willing to search around and be flexible with dates to actually get them to line up. And even then, you have to assume the 2 units won't be right next to each other and may be on other sides of the resort, so IDK if that could even work. So you might be looking at an entirely different system for 3BR. And finding and booking those are even harder because they're kinda rare.
For instance, I know Wyndham has Emerald Grande in Destin, FL. Those have a lot of 3BR, but they cost a LOT of points, like 650,000 (note every systems points values are unique and don't translate at all). LOW Wyndham MF/pt (without the program fee) are around $6.20/k so that's AT BEST going to run you $4,030 in MFs before program fees each year. If you get the Club Wyndham Access that are given away on ebay (so almost no acquisition fees), they are I think getting close to $9/k so $5,850 MFs. IDK if Destin, FL would even be worth about 6 thousand a year to you. Of course, that's a very expensive example, but you can look at each resorts points costs online for Wyndham, and probably HGVC and Marriott also.
So, like many say - the best thing to do is consider
where and when, check what size unit or how many units you would need to have 8 people, ask on TUG if those dates and units and locations are likely to be easy to strategically book or if you'd need to own there, and then see the yearly costs, and if you're still thinking this is worth further consideration, look into the resale costs to make that happen.