Originally posted by Murfy so if I have spot metering on a manual lens, it uses the center to get the spot meter reading, so the link ae to af point option is basically null?
Yes.
Originally posted by Murfy if I use spot metering on af lens but have the link ae to af point off, it spot meters in the center, no matter where I set the focus?
Yes. By default, spot AE metering meters a tiny 5% of the scene dead-centre in the frame. And according to the manual, it's fixed there. If you have 'Link AE to AF point' turned off, the camera will have no reason to do anything different.
Originally posted by Murfy I mostly use spot metering, sometimes, center weighted, and some old manual lens. if I use matrix metering and link ae to af point (on af lens) then it doesnt really matter either?
If you manually choose spot metering as the AE mode, then 'Link AE to AF point', it would be logical for that 5% metering spot to follow around your AF point (within the coverage area of your 27 AF points). Ditto for if you selected centre-weighted metering together with 'Link AE to AF'. And in multi-segment metering mode, when setting 'Link AE to AF Point', it would be logical for the camera to bias the exposure reading towards wherever the AF goes, rather than meter across the whole scene.
So sure, with AF lenses, sometimes using 'Link AE and AF point' might make manually selecting spot metering or centre-weighted metering redundant. With the 'Link AE and AF' option, you can just leave the metering mode at the default 'Multi-segment' setting, do your AF and rely on the 86k metering sensor to follow where you focus.
But it is also possible that the metering mode you select first (Multi-segment/ Centre-weighted, or Spot) may override or limit the scope of operation of 'Link AE and AF Point'.
This is one of those areas (like AF-C) where the K-3 has a ton of advanced features, but unfortunately there isn't a lof of detailed information about how they work in the manual. So I am just taking educated guesses here.