These are my Research plans.
In the Infantry category I am pretty well caught up so I only need to research Marine Infantry. This will allow me to produce a Marines which have a lot lower amphibious penalty than most other units.
In the armored category I am researching light tank armor. TH increases the toughness of my light tank, motorized, and mechanized brigades which makes them more resistant to damage. However it also slows them down slightly. Researching this tech will also allow me to research medium tank brigades as well.
In the naval escort department I am improving my destroyers Guns, Armor, and engines. Gun will increase the firing range and damage my destroyers inflict. Armor will make them more resistant to sinking at the expense of speed and range. Finally engines will increase my speed and range but will increase my fuel consumption.
For my capital ships I am Improving my ships AA guns which increase their air attack and my secondary guns which increase naval and air attack as well. Eventually I will improve my carriers tech which is not that good but i want to improve my Air defense first.
For Bombers I am researching a basic bomb which will increase soft attack (against infantry and trucks ect) and their hard attack (against tanks) values slightly for all planes. Later bombs will only got for certain plane groups. I am also researching a medium fuel tank which will improve my tactical bombers attack radius at the expense of survivability.
In the Fighter category I am researching Multi-role fighters which will allow me to construct these planes. While having slightly less air attack than interceptors, they have more range so I can attack enemy air forces inside their territory.
For industry I am researching ways to increase my production and my production efficiency. The first grants me more Industrial capacity to build things while the second lowers production time and cost. I believe it also lowers resource requirements as well. ( a Factory or IC need 1 unit of metal, 1/2 unit of Rare materials and 1 unit of "energy" to work effectively) I forgot to place in the screen shot that I am researching Supply production which increases the amount of supplies I get Per IC devoted to producing supplies. I am also researching new ways to break enemy codes which increases my ability o hunt submarines and also gives me an advantage against less advanced opponents in combat.
In the new category for unique German tech I am researching advanced optics. This leads to 4 technologies that improve the optics of Tanks, Armored support Vehicles such as assault guns, self propelled artillery and tank destroyers, Artillery, and Ships. The downside is that thee tech all increase supply requirements and lower my production of rare materials and metals.
Finally I am researching Elite mobilization which grants a one time 10 % bonus to my leadership value which should allow me to research more technologies at once.