Correct, banked or borrowed points cannot be transferred to another member.
For you, since you own Trust points, I would recommend renting from somebody who has clean (not banked or borrowed) Trust points for rent. You can rent in multiples of 25 points. The reason I say rent Trust points is that the way the system works, is that you need the same type (Trust or Legacy) of points for each room night, so it will just make the ressie easier to book if you have all Trust points.
You can book a ressie with a mix of both, but oftentimes, the mix will not work out perfectly, as again, each night needs to be booked with one type or the other type (not a mix) so you can end up with issues of not having enough of one type...and a little too many of the other.
If you do end up renting Legacy points (as they are usually way more plentiful), then just make sure you rent in increments of single night rental needs during the time you plan to book your ressie.