We have, of course, already had experience of the 5 substitutions rule when the EFL introduced it mid-season in November during the 2020-2021. Interestingly, Argyle did not always use the all five substitutes option. Primarily the times they did it was when we lost 1-5 to Fleetwood, 0-4 to Rochdale, 0-3 to Bristol Rovers, 0-3 to Peterborough, 0-2 to Northampton, 0-3 to Hull (but not the 0-6 to Charlton!). Clearly, the substitutions did not change those games nor did they manage to score (apart from the OG at Fleetwood). We did, though, use all five in the 4-3 win v Lincoln but none of the substitutes scored.
These games were of course with restricted attendances which may have given a false indication as the crowd's reaction can often inspire a substitution if a player is having a mare. The evidence would appear to be under Ryan Lowe that the use of five substitutions made little difference to the eventual result. Under Schuey I detected a better use of substitutions but that may be because the team were playing well and not in a downward spiral towards the relegation places as in the previous seasons.
It will certainly be interesting to see if we can impact a game with judicious additional substitutions to either win a game or secure a game but I wonder whether we will, after all initial judgements, notice any difference in the outcome of results compared to the use of three substitutions.