Separate Power Supply on Sensors?
If you do not daisy chain your ICs, then it should work well enough.
Yes you need decoupling caps. With them any fluctuations that might occur will not affect your power supply and thus rest of your circuit.

As far as choosing a linear or a switching regulator, give it a read:

https://www.digikey.in/en/articles/techzone/2017/sep/understanding-the-advantages-and-disadvantages-of-linear-regulators