Is it ok to pair 11-36T cassette 11 speed with 50-34T Crankset?
The Shimano 105 RD in its latest 7000 version has an 11-34 tooth capacity in the long cage version. So theoretically at least, Shimano is rather conservative concerning those limits, the answer is no, you can't. With some tweaking of the b-screw it might be possible but you will have to take the blame if it doesn't work.

This said, the 34 to 34 pairing gives you a 1 to 1 ratio that allows for steep climbs, and is rather demanding in pedalling cadence to keep up enough speed for balance. Example: riding at 6km/h in the 34-34 gear requires a 74 RPM cadence.

Technical details on the the 105-group to be found here:

https://bike.shimano.com/en-US/product/component/shimano105-r7000.html