Editing and Adding Challenge(s) - Architecture

I am unsure how to exactly tag this post but I think it's more of a design type thing. There is a tech side that I want to write about which more or less came during the development up to this point.
What am I exactly talking about? I am talking about how there were multiple variables (and some i'm not thinking of yet) that control how much something increments or how much some number gets modified all throughout the code. These variables were created out of necessity and not out of pre-planning or prediction that I would ever start writing a system that would allow me (& hopefully ya'll) to create challenges to play with different values for these game variables.

So I guess I just wanted to write out that I have just found it quite useful to just write say a scoring system where you just have the score's modifier be local in terms of stack scope to where the score is being "judged" ie modified by the value.
Example is like

{
integer or float Modifier = 2;
LongTermScore += RecentScoreMade *  Modifier;
}//Modifier drops out of scope so it's irrelevant long term

I could've actually tried to predict the notion that I would want to change the modifier long term like I do now, but I would've ended up writing something completely different and would've deleted it today.

So that's the tech rant part I guess. If you disagree or think what I wrote is unclear, please comment to discuss or let me know I need to clarify what I mean here!

The design part is more so what of the many variables should I let myself (& hopefully ya'll) change?
I could make it so the size of the combo buffer changes to be larger or smaller, but is that a good idea?
I could make it so the score modifier can be changed, but is that a good idea?

I try my best to seriously question if making the "changeable" actually changeable as by changing it, it will have a serious impact on the game's final version. Reason why I think that is due to how complex the game already is despite being so simple by appearance. One tiny value change could make some strategies sooooooooo much easier to do or soooooo much harder to do or so I have observed by just changing some values like gravity by a largish amount.

Oddly enough, it helps me to think of a game as just a simple collection of math functions who's results get inputted into each other making this extremely monsterously gross daisy chain of math functions which ultimately is your game. Luckily these theoretical math function calls don't cost any processor time since it's just a mental model here :)

Sorry for any grammar errors in any of my posts btw. I do one read over before posting to hopefully get all of them errors fixed but don't catch em' all sometimes so lmk if there are any / let me know what your thoughts are on anything I wrote today!

Have a wonderful day, please!