The basic airframe kit has had a few small evolutionary changes but nothing that changes function, speed or efficiency. These are things like incorporation of the few SB driven changes, fuel valve change (longer handle shaft), fuel valve location change (lower in the tunnel) fuel system plumbing (fitting at the tunnel sides vs just a tubing exit), etc. The non-SB driven changes are really just minor improvements to the construction process (easier to fab fuel lines, easier to route rear seat heat SCAT in tunnel, etc).
That said, there are a LOT of after market additions/mods that can be incorporated now that weren?t available in the early days. This includes things like full electronic fuel injection and ignition, different fuel valve, different fuel pump(s), electric heat & oil door actuators, tunnel access panels, full interior finish kits, rear seat options, overhead consoles, air conditioning, higher capacity brakes, flush exterior door handles and pretty much anything else you can think of.
A Lycoming IO-540-D4A5 is the same today as it was decades ago as long as it is a stock engine (except for the shift from narrow deck to wide deck in the 1970s). Many replace one or both mags with electronic ignition and some replace the fuel injection system with electronic injection. Lots of chatter about HP differences based on dyno runs but little real world head to head performance data. Electronic ignition seems to get slightly better fuel economy, mainly from being able to run a bit more LOP than without it. 3 blade props seem to have a bit better climb performance and slightly lower top speed than the BA 2 blade Hartzell. You?d probably be hard pressed to find any RV-10 in the fleet that is measurably faster than others.
Vans originally planned to support a Continental IO360 (210 HP) in addition to the Lycoming parallel valve 540 but after a survey of early builders, the Continental was dropped as an option and no FWF kits were ever sold for it. The fleet consists mostly of Lycoming 540s but there have been at least 3-4 Chevy LS-1 conversions and at least 1 Suburu conversion. The Subie conversion (that I?m aware of) no longer exists and I believe that at least a couple of the LS-1 conversions were removed and replaced with Lycomings, I think there?s at least 1of the LS-1 conversions still flying though.