Since we have to start somewhere, here's a question for you. Did the problem exist prior to replacing the fixtures?

You're implying the shower mixer has anti-scald protection...does the sink as well? Further, if a plumber did the work was there a mixer installed at your water heater?

Since the system is well supplied (excuse the pun) do you know what the drawdown volume is, and where the pressure band is set (20/40,40/60, etc.)?

Try not to conflate volume (flow) with pressure (force).

I think we found the answer. It does sound like you are right that it's volume I'm concerned with and not pressure. The sink doesn't have the anti-scald, and the water heater doesn't have a mixer. What we do have is a water filter after the water pressure tank from the well. My husband changed out the filter and now my water volume (flow) is the same from the hot water faucet even while the water is cold. Now I'm not sure why it increased when the water got hot, but it's working the way I'm used to.
Thanks for clarifying the difference between volume and pressure. Our pressure is low. I think around 30, so probably 20/40 at the pressure tank. But volume isn't typically an issue.