Excellent work @PhlebasthePhoenician. I previously said that Friendlies counted as first team games up to the first season of league football, but that was just for the match lists in the book. For stats purposes, Friendlies are included up to the First World War.
I have found Dave Finch’s list of what he included as “First Team” and that is what WWEPA base their stats on.
1887-1914: All games.
1919-1939: Spartan League, Isthmian League, FA Cup, FA Amateur Cup, Berks & Bucks Senior Cup, Bucks Charity Cup, Oxford Hospital Cup, Maidenhead Hospital, Cup, Berks & Bucks Benevolent Cup, Windsor Hospital Cup
1939-45: Great Western Combination & Subsidiary Cup, Berks & Bucks (Emergency) Senior Cup, Berks & Bucks Red Cross Cup
1945-85 - 1986/87: Isthmian League, League Cup & Charity Shield, FA Cup, FA Amateur Cup, FA Trophy, Berks & Bucks Benevolent Cup (1945/46), A. F. A. Invitation Cup, Smith Memorial Cup, East Anglian Cup, Wycombe Floodlight Cup, Mithras Cup, Anglo-Italian Trophy, Anglo-Italian Semi-Professional Tournament.
1985/86 - 1987-93: Gola League/Football Conference, League Trophy & Shield (Bob Lord/Drinkwise), FA Cup, FA Trophy, Berks & Bucks Senior Cup, Inter-League Trophy, Isthmian League Charity Shield. Capital League is not included.
1993 onwards: All Football League competitions, FA Cup, Conference Shield. Berks & Bucks Senior Cup is not included.
Dave’s notes on some of the other cups and leagues:
Cups that involved entering and had more than one round generally have been included, as has the Isthmian League Charity Shield (you have to earn the right to play in this). Not included are friendlies since 1914 or one-off invitation cups, like Wycombe Hospital Cup or Battle of Britain Cup, as these would sometimes include representative sides (e.g. 1957 XI in 1965) and guest players, so these are counted as friendlies. Also not included is the Premier Midweek Floodlight League and Shaw & Kilburn League, as these effectively took the place of the reserve team and registration of players was flexible. In PMFL, against Hillingdon (4/5/70) several Reading Youth team players were used and at Chesham (15/4/71) the entire Flackwell Heath team were used. The Wycombe Floodlight Cup was a first team competition (except for Reading reserves in the first season in 1965/66) and, in that first season, there was actually a reserve section.