Best to get started with the fz150. It's a great starter learner bike. Parts aplenty, and any shop can fix it.

A next jump up would be a used Dominar 400 if you plan to go with a Full B license. The dominar is top heavy and  heavy bike for the engine size, matching 600cc bikes. If you get used to the weight of the dominar, the rest of the bigger bikes will be fine.

Mentioned it before, the z650 I took my test on is easier to ride than my dominar so the test was easy for me. I picked up a dominar when I got my L last year.

You will eventually get used to the weight of a bigger bike.

If you are planning to get into bigger bikes in the future, No point getting a kapchai (even the bigger 150 clutch ones) as the handling characteristics of a kapchai is different from a full frame bike.