Tiling over areas with slight movement

We are planning to tile over a large (about 7m x 7m) area that was previously three adjoining rooms - the old kitchen and dining room with an extension built across the back. All three have been recently re-screeded to get them to the same level. Planning to use large format tiles and looking for advice on whether we will have problems long term due to:
(1) The extension was built on block and beam and is not totally rigid: you can feel it bounce a little in the centre if you jump up and down though not nearly as much as a typical wooden floor. Have had opposite advice in tile shops, so just wondering if 600x600 tiles are sensible, and if flexible adhesive or something else is needed.
(2) There are joins, with expansion strips, in the doorways (2.5m) between the rooms. There is definitely some relative movement between the different slabs of screed, I tried to measure this and would estimate as little as 0.1 to 0.2mm. Once again I have had varied advice - so wonder if 600x600 tiles will be fine, with flex adhesive and grout, if I should make sure tile joints line up with the screed joints, or something else. Should I try and tie the slabs together?
Opinions and experience welcome!

I would suggest using a ditra mat to help decouple the movement from the tiles.

https://www.schluter.co.uk/tiling-on-cracked-and-green-screeds.aspx

Thanks, ditra is a good suggestion, it will add to the cost (I assume I have to do the whole area not just a strip in the doorways) but the main issue is that levels have been carefully calculated and another 5mm will definitely be a problem...
There are some other thinner decoupling products, but they don't seem to have the reputation of ditra.

if the floor ha movement you will be having problems at a later date, tiles cracking, grout cracking out, adhesive coming away from subtrate, best way around it is to fit a decoupling mat, quite a few on the market but without one you will run into problems and a good flexible adhesive and flexible grout