I have a machine similar to yours. Table 9-1/2” x 31-1/4”
This is what a 5” vise looks like on it, I’m pleased with the size, a 4” vise would also be fine IMHO.
I got the vise on Amazon years ago, it’s very accurate for a knock-off, maybe I just got lucky.
I’ve never used the swivel base that came with it, but a member here has fixtured a rudimentary poor man’s rotary table with his swivel base, & If it doesn’t add much $$ & you have no RT, buy it.
I would also avoid Vevor, i purchased a 5” 3 jaw chuck from them for very cheap, bad idea, probably will offload it with a full disclosure.
And I agree, buy the best vise U can afford.