Yes will affect the performance so u have to keep the memory below the full capacity of the internal storage

If its not working properly after the update samsung will provide software update to fix it

Check the OTG cable/adapter are compatible and then connect the OTG device to your phone

In future samsung wont bring memory card slot back to its phones because the internal memory provide faster speed for accessing data than the memory card, so choose ur mobile phone with 128gb ,256 gb or higher internal memory based on ur requirement.

There is a side effect on using hotspot ur mobile will drain ur battery fast and become more hot .its not good to use hotspot for a long period of time.