Show me some numbers! ;-) … Perhaps I miss something, but basically we have 32bit pointers vs. 64bit pointers, the rest of the data should be the same size. 64bit should be faster for tasks where the CPU is the bottleneck/computations, so IMHO it will be an interesting tradeoff with no clear winner for me.
I don’t know either, but unless one uses zstd (lzo seems more like a thing for this hardware), I would hope that it is totally usable. (Running zstd memory compression on a Raspberry Pi 2, w/o any noticeable speed impact)