I assume you refer to its performance. Yes, it will.
However if you don’t have the HW yet I’d suggest to go with a RPi4 as that’ll be what most others do, “extinguishing” the RockPi as a potential source of problems.
There’s ways to deal with SD wearout on that as well such as ZRAM or USB-attached SSDs.
Going RPi4 will also allow you to go with the openHABian image.
Yes, use 32bit Java, 64bit has no advantages but IS slower albeit math performance is irrelevant in home automation application.
Size? Dunno, and depends on storage mechanism. Just start and learn. You can and will adjust parameters anyway so one cannot tell upfront how much space you’ll need, but very likely ANY SSD will do.