I notice you always throw an extra engineer unit, can you tell me the reasons why?
Also thanks for the help and advive!
Basically what achpawel said.
Engineers are super cheap, give you capping power and with a flame thrower they become your CQC unit and have decent damage output as long as you don't run them into enemy squads over open fields. Also tactically you should get used to mine placing, and the second engineer will make it way easier. And you can always go full cheeky-breeky and build a demo charge (90% of the players never turn the camera. So turn the camera and build the demo on the hidden side of the building. Big bushes work very well, too).
You can build a second engineer right from the start when you play with Penals. Send the first engineer capping right away, build T1 with the second engineer and you should hit 300 MP when the building is finished. It's a viable build, and allows you to have squads out on the field quickly to compensate for expensive Penals. With this build an early flamer is almost mandatory. However you can just build 1-3 Penals and go for the second engineer any time you want, that's also good.
The Conscript merge function is very good with flamer engineers and requires a bit of micro. But as long as you don't run into an MG, you basically have a 10 men flamer squad.
The second engineer can later be upgraded with a sweeper when the LV phase begins and is very important to push up with your T70 to keep it safe from mines. Two engineers allow you to repair your T70 and all subsequent vehicles faster. And you need two engineers anyway for the late game. If you're lucky you can vet at least one of them to vet2. Keep that one alive at all costs since it repairs way faster. Don't sacrifice that squad and use it for back line mine placing only.
I usually go for one engineer with flame thrower and one sweeper. However with the new patch I often found myself building two sweepers for the improved repairs.
Now that said and counting all the advantages of a second engineer: It's also perfectly fine to build it only in the late game. One big disadvantage is that you invest 170 MP into what is probably the worst fighting squad in the game. If they get into a fight, park them behind cover and make them hold out until a real fighting squad arrives. But nevertheless they're decent to make MGs move if they flank them. Most Axis players will move the MG even it gets flanked by just an engineer which could be fought off by other units.