I have a Topstone alloy 105 also and I have considered the same changes. I agree with SteveB. that the crank is a a very marginal gain unless you make a drastic change to the gear range. Wheels are something I am looking into for my bike as I would like to have the added benefit of a different set of tires that can be easily swapped out. I do not have any hands on with the GRX though it does look interesting. I will be interested in seeing what you ultimately do and how it changes the bike for you. Personally I am so happy with what the bike is as stock I am reluctant to make any big changes other than the stem and seat.
Frank.