None of the BESM games seem to suit that purpose
(based on popular opinions found on the internet)
I have no experience playing that system, but given the lack of reply with such a high bounty I'm assuming neither do most. Further I haven't conducted any analysis of the rules, but rather did a quick google search to see if a pattern emerged in popular opinions.
As pointed out in the comments by @KorvinStarmast this question about balance had people answering:
MadMAxJr: "Unfortunately, in my experience, BESM can get very lopsided in terms of balance.
Most balance in BESM has to come from a mutual agreement between the GM and players to agree on what is overpowered."
Paul Marshall: "This problem exists in just about every kind of build-points RPG, and the usual solution is lots of GM input during character creation. Either put a hard limit the maximum power that characters can take during creation, or find some kind of consensus on what's overpowered"
Further this trend holds true in other online forums, such as giantitp:
tyckspoon: "From a mechanical perspective, the system is pretty much broken from the start (in far more obvious and easy to implement ways than D&D.) It takes a lot of discussion with the rest of the group and the DM to avoid ending up with a set of wildly disparate power-levels in the characters." (talking about BESM d20)
or over here at the brilliantgameologists:
Fox Lee: "I would not recommend BESM 2E. It has some interesting principles and I quite like the Body/Mind/Soul stat system - but it's horribly, horribly unbalanced, and shortsightedly takes the stance that the lack of mechanical solidity will be compensated for by the players being sensible. Oops. Seriously, do not play this game with a min/maxer who's even vaguely good." (talking about BESM 2E)
Kari "[BESM 3E is remembered as] somewhat more balanced. Still needs a GM with an iron fist to ensure none of the players get too far out of hand, though."
Or here at forum.rpg.net about BESM 3E:
wuxiasnake "I know the nature of points buy effect based systems makes them inherently open to abuse by munchkins. The reason for my question is that 2e was far too easy to break by accident."
Marius B "It's just as easy to inadvertently build an overpowered character in 3e as it was in 2e."
I read repeatedly that with a good group and GM people had fun with it, but
Fox Lee: "Creating balanced rules shouldn't be up to the GM. That is the system's job. Obviously, any system can be broken by a GM tweaking it, but it should be at least reasonably balanced before the GM gets his/her paws on it, and tri-stat BESM isn't." (talking about Tri-stat)
This is especially true for people intending to optimize, because hearing "No" after you spent all that time and energy looking for a synergistic combination can be frustrating, potentially putting you back to square one if the forbidden piece was essential to the build. Again I have no experience of my own with this system, but based on theirs (and other posts like these in the threads) it seems to be a rather crazy system, ideal to have a crazy kind of fun with, but not at all suited for purposeful optimization.
I believe this is an X-Y Problem, where this question (y) is your attempted solution ("does BESM work for me?"), and your real question (x) is "Which system is suitable for optimization play?". Since shopping style game recommendation questions are no longer considered on-topic, this real question is best answered in a forum. Ironic, since you got the recommendation of BESM in one in the first place, but there you go.
An answer that came up a lot during my search was "Why not play X?" recommending various other systems (none of which I recognized). Maybe check the links to the discussions and see for yourself. However note that those too would be X-Y problems, as people in all these threads were asking about BESM. Consider making another thread specifically asking X in a relevant forum (follow the link for a selection).