The most simple, sensible article on encryption strength you'll ever read

https://medium.com/@drgutteridge/whats-the-deal-with-encryption-strength-is-128-bit-encryption-enough-or-do-you-need-more-3338b53f1e3d

Just a bit from the above:

'First thing is, don’t panic. The claims made about the capabilities of
code crackers are usually exaggerated. As Edward Snowden said, ‘trust
the math.’ Mathematics is a fact. The NSA is constrained by it as much
as everyone. So we can take a look at the math and draw some
conclusions.

One simple fact is that each bit you add to a key doubles the number of
possible keys and hence doubles the amount of time it takes to try all
possible keys, i.e. a brute force attack."