Basic members outnumber premium by a decent margin. For players playing exclusively in the random pools, i.e. primarily not in club events or tourneys, I would generally expect similar percentages across a large, random sample of players.
As to it impacting ratings, any effect is likely to be small, in my opinion. While the premium pool is smaller, any inflationary impact would be mitigated by the fact the playersw would still be getting paired with basic members with similar ratings ranges. If the results of those games were statistically deviated from what would be expected, then there might be something to it.
Looking at an arbitrary archive of a paying member may not tell you anything useful. A premium member may be playing a lot of games within clubs that are premium only, or have a higher ratio of premium memberships compared to basic, so that could skew results.
There are some pairing processes that attempt to not pair higher lag players with lower lag ones, and will pair players in the fair play pools (lots of disconnect losses, making players wait in losing positions, etc), so there is a selection being made in those instances. Other than that, the random pairings are based on seek parameters, with an attempt to pair compatibly within those constraints.
I'm not saying that there isn't some part of the algorithm that might not pair premiums more often. I'm just a member, and have no special insight into the inner workings of the system, other than what is published in the help articles or has been posted about by staff.
https://support.chess.com/article/369-how-does-matching-work-in-live-chess