Just my opinion here. Partial Mashing is all the work of All Grain, and also has the negative aspects of extract. I’d recommend Just going BIAB.
I typically brew 3-gallon all grain batches. I mash in a bag in a cooler with plenty of room. I’m not sure how small you can go, but it looks like @uberculture covered that. For the boil, I use a 20-quart pot. I start the boil with about 4 gallons; the threat of boil-over is pretty scary at the start, but it gets the job done.
Our host has a VERY small selection of kits at the 3-gallon size. My favorites are the Dead Ringer, De Belge, and Kölsch, I’m that order, YMMV.