It's a local clash for sure, but not a derby, for the reasons you go on to say. The problem is the word 'derby' has become so undermined by marketeers recently (The Southampton v Bournemouth "New Forest Derby"???? Give me strength...) that it has begun to lose all meaning. It was taken to the extreme in 'The Hundred' this summer when I heard one of the commentators say 'Well for a London Derby, the crowd here for Spirit v Invincibles is not very partisan'... FFS they had invented these teams when down the pub one night, just because you call it a derby it doesnt mean it is one.
I want us to beat Wycombe, I'll be in a bit of a grump Saturday night if it hasn't gone our way, but I'd take us losing 5-0 to them twice this season if we can finish top 2.