Thanks for the replies. I wanted to try some of that focal length of 80 - 200, crop factor included. But I'm worried about shooting handheld with it. (fuji x series isn't really a fan of IBIS). My curiosity started when I saw this
SMC Pentax-M 80-200mm F4.5 Reviews - M Zoom Lenses - Pentax Lens Reviews & Lens Database being sold near me at £30 and seems to be in very good condition, but the lens appears to be a push-pull type of zoom, hence why I'm worried about handling. Of course, I could always compensate one way or another but shutter speed or a tripod (which I'm trying to avoid). But I also saw the Pentax F 80 - 200 which, I gather isn't the most popular of the Pentax lens line, but the plastic build and the in-body zoom mechanism make for a nice compact, light version of the Pentax M I gather.
I don't mind shooting manual, I've used M42 lenses and 7artisan 9/10 times more than my kit lens XF 18-55. I'm worried if this Pentax F lens can work manual too if adapted to a fuji X. I cannot find a lot of info about it sadly.
Also, I've dabbled around the idea of getting a Pentax camera but that's another set of research and a whole new system. (and I don't know if the pentax K-s1 is any good).