What else would there be that could be a concern?
If a plugin is adding noise (which is stupid for a plugin to do) then I guess you have to consider cumulative effects. But there’s no inherent noise or distortion added in the process of passing the bits from one plugin to the next. If I put 10,000,000 reaEQ’s in series, the output would be identical to the input.
I personally think loudness metering gives itself way more accolades than it deserves. Even the best loudness meters can sound wildly different in loudness with the same measurement.
What it does offer is familiarity to people who spent 40 years looking at VU meters and having an intuition for what they are measuring. VU meters are not a gold standard. They are just what happened to be an ok solution 50 years ago, so some people got used to them.
Think about what you actually use meters for. In a broadcast situation, you get a feel after a while for how your meters should be showing in certain situations. If you are dealing with spoken voice being broadcast, and you are constantly using whatever meter you have, you get accustomed to what that meter should look like when levels are good. That doesn’t mean that I wold want to take that same meter home and use it to measure the loudness of my guitar track. I’d have to relearn the meter for that situation anyway.
I’ve tried a million different meters. In the end, I always end up going back to the default meters in Reaper. Not because they are better, but because I’ve seen them enough to at least know what they are telling me. That’s worth far more to me than somebody’s loudness algorithm, which in my experience, is largely bunk anyway.