Attiny 45 - Timer based input capturing vs. pin change interrupts

Ok.

Can you provide this information? It may help select a micro controller that will do EVERYTHING on one chip.

As a table:

Column 1: The sensor or modules name / Part Number
Column 2: The Output or Required Pins.
Column 3: Specifics of the dataform (frequency for example).

The whole thing will probably be do-able on 1 MCU and with some code squeezing (like avoiding floats) should probably be fast enough for a good update rate on that i2c screen.

You are investing a lot of time in a "multi-IC-network" like idea, but I just feel it may be added complication and could lead to all sorts of errors...

If you are determined to have more than 1 MCU, then can you draw a clear schematic (hand drawn or whatever) so we can sort of actually "see" than trying to read what you are attempting?