I kind of understand how EV (blue numbers) and IV (orange numbers) works, how IV are set values while EV can be increased or decreased and how EV total is 510, single stat max is 252, etc. I also understand how nature works, one additive stat one subtractive stat. What I don't understand is how all (especially EV) affects the Stat Total (white numbers).
Here's a situation:
Say i have 2 pokemons of the same kind and they both have the same nature, same IV, and same EV (say 252 on atk and spd and 6 on hp). The only difference between these two pokemons are they're different levels, one pokemon is lvl 20 (mon A) and the other is lvl 30 (mon B). Because everything is the same except level, the Total Stats between the two are also different (I'm assuming mon B has mostly higher Total Stats because of level advantage).
Say I level up mon A to lvl 30 to match mon B. Now, both pokemons will have the same nature, IV, EV, and level.
My question is, will mon A have higher Total Stats than mon B at this point (both lvl 30) because it had a "headstart" with max EV's? Each time mon A leveled up from lvl 20, did the EV's affect the Total Stats to where there is a difference between mon A and mon B at lvl 30?
If the answer is yes, how come people have said that EV training a pokemon doesn't matter what level you max their EV's as long as it is before lvl 100? Wouldn't it be more beneficial to EV train a pokemon at a relatively low level so it can have this advantage/headstart?