Shaun,
I too use Lr HDR a lot with my Fuji X-T2 (until the X-T4 is delivered). It works well for 90% of what I shoot
I usually shoot 3 exposures that are 2 stops apart or -2, 0, +2.
I'd be shocked if your A7R3 didn't have more dynamic range than my X-T2 in each shot.
Have you tried what Mike suggested about using "Auto" in the Develop Module? It in the "Basic" section.