My L/R balance averages around 46/54, but varies much more than that on short efforts, or when tired. If you’re looking more at tracking fitness trends over time though, I wouldn’t think it matters so much. A single sided meter will certainly be more accurate than HrTSS.
I had an SRM which didn’t quite live up to it’s “gold standard” status. Now using a Rotor 2Inpower which has been brilliant, although over budget. I think the single sided Rotors would be within range if you shop around.