Your idea of contact printing sounds completely legit 🙂
However before you decide on a format or camera let me propose following:
1) Have a look at the images you have taken (with whatever camera or format) and select a few of those which you think you would/could take with 5x7 (or 8x10 or 7x11 or 5x12 or whatever)
2) print a few in a couple of sizes that would match the formats you consider. Of course in BW 😉
3) have a look at the results, hang it on a wall or whatever the plan is and reconsider.
4) Once you made a choice (or at least a strong preference) only then start to worry about WHAT do you ned from the camera and start to look for one that gives you what you need (movements, bellows draw, lenses).
5) reconsider whether what you plan is doable (time, money, size, weight ...) :angel:
6) Go for it and enjoy.
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I can only say that 4x5 is too small for decent contacts - my personal experience and feel. 5x7 is a lovely aspect ratio, 7x11 would be heaven ... for me 😉