It seems that the newly installed 1.7.10 pack I installed, does only launch Vanilla 1.7.10 Minecraft. I checked the jvm arguments, giving it more RAM does not make it work, and the path points to the correct instances folder.
The modpack in question is called "Catalyst" and I installed it in Modpack version 1.4.2 in the newest overwolf curseforge launcher version.
I am still using the launcher thats not from the microsoft store, and am using a mojang account. I have JRE and JDK 16.