What's the wattage of the mosaic mini pendant? I would think using the light that mimics your vent hood would probably look okay if the sink isn't too close to the peninsula, assuming the wattage is high enough of course. The only concern I would have is a pendant over me instead of over the sink area; might not give appropriate light. Is the vent working? If not, could you take it out? Or maybe doing two smaller recessed lights on either side of that vent (depending how big it is across your sink area) would work better; then you would have the light properly over the sink? Hope those thoughts are of some help...

I wouldn't exceed 6" in diameter. Depends on your ceiling height as well. However, if it is 8ft or so I'd stick with 5 to 6" in diameter depending on your space. I'd select fixtures that work best for the space. If there is not a lot of other lighting in the space then you want open or clear glass lights. If there is decent light from cans or..... and you want down lighting you can select cones or similar in metal fixtures.

Typical height over a table is 30”, and island/peninsula is 36”. Top of counter to underside of fixture.

You electrical right there with the boob light , whaich BTW needs replacing. Any 1/2 decent electrician can run the electrical from there for the pendants and use all LED bulbs then one circuit can handele a ton of lighting and not those really ugly bare bulbs and If that is too much money then do a nice LED track light that either curves or articulates to get light where you need it.