They have almost no differences in performance irl. Around 600 RPM for both weapons and 20 round mag. The FG42 was just designed better and more expensive but that's about all.
The theoretical ROF is usually no indicator on the actual combat effectiveness of a weapon.
The BAR and the FG42 are extremly different pieces of kit and are hardly comparable. Depending on situation one is better than the other.
The BARs ROF is significantly lower than that of the FG42. The A2 version of the BAR wich is the one widely used during WW2 cycles with less than 500 RPM. Combined with its high weight of allmost 9 kg it made the gun very controllabe in automatic fire. The BAR as such also is very accurate since its more of a full auto rifle than an LMG.
The FG42 has a ROF in the 700-800 RPM range. Combined with its low weight ~5 kg and the powerfull ammo its allmost uncontrollable in full auto. Standing unsupported its difficult to keep short, controlled bursts on target. The low mass of the gun combined with the high ROF will make it heat up quickly. Its not suited for sustained fire. Much less than the BAR. In single shots the FG42 is quite accurate.
The low weight and the faster realoding due to better ergonomics make the FG42 more mobile and a better assault weapon though.
The FG42 is more of a full power assault rifle than an LMG.
It's like comparing an AK47/M16.
Wich are again two completly different weapons wich are designed with completly different doctrines and concepts in mind.
To put it short and blunt the AK47 is a high powered, glorified SMG wich is cheap and easy to produce and maintain.
The M16 is a highly accurate, lightweight, small caliber rifle.
I think it would be best if they adjusted the BAR in cost and effectiveness. A dual BAR rifle squad should overwelm a MG42 armed Grenadier spuad at short range but loose at long range. The BAR should perform more like something between G43 and StG. Two BARs should be more expensive than on MG42 upgrade but one should be cheaper. About 2/3 at max.
The Bazookas are currently a joke. No doubt. I am ok with the fact that they are ineffective against heavy armor. So rifles can only play a supporting role in this case. But they should reliably hit and kill light vehicles and light armor. I have seen Kübels getting hit two times by Bazookas and survive. Combined with the fact that the accuracy of the Bazookas is atrocious, so two hits are likely a two digit number of shots, that can't be right.
Same method as with BAR pricing. One is cheaper than a Schreck 1/2 - 2/3 and two are more expensive. The penetration can stay the same but the accuracy should go up.
I also think the Schrek is too accurate. The upgrade of the Volks is a plain buff IMHO. It increases the output of the squad in any way. The Schreck is better against infantry and support weapons than the rifle it replaces is. The Schreck has a very bad tendency to snipe soldiers or kill several at once with its splash. Even more so if the using squad gains vet.
It reminds me of the CoH1 PE Schreck blob. Who would fire a alpha stike of 8-10 rockets and kill half of you infantry by doing so. This was rebalanced and taken out for a reason.
The Schreck should only be able to hit soldiers at short range. About SMG short. At medium it shoudl be able to hit support weapon teams with its splash. At long it should have a 1/2 - 2/3 hit ratio against medium tank sized targets. This of course improves by closing in.