I remember older discussions which demonstrated that - provided the crit rules are followed properly - it makes no difference how crits are distributed in one location, as long as they're in the right location. (Short form - if you're rollin for crits in the torso, rolling "lo-hi" and then location, if you get 'empty' or the like, re-roll both dice.
So for most cases the TRO details can provide you with enough details to make a legit record sheet. Arm crits being a potential issue though, true.
You'll find free design tools like MegaMekLabs and SSW provide the ability to quickly print record sheets. These are, on the whole, accurate, as far as they reflect the current state of rules & equipment. But at a con, or Demo Team game, they'll provide copies of formal Record Sheets, as there used to be a whole range of bugs in design programs like them, or HMP, which could be exploited.
The one thing formal Record Sheets are the only source for, is placement for variants mentioned but not statted in TROs - essential for kitbashing & accurising. Oh, and playing, too ;)