Helgen is the very first place, where you define the character race and gender etc. The castle with snow is well into the game, and is not an optimal place to start adding mods, as mods can affect and contradict what is already in the savegame files. Once you get your mods set up and understand whats going on, you can add and remove mods as long as you do it "properly" but to start, you want to reduce the number of issues, hence the recommendation to start a new game. If you have the NON Special edition version, you do NOT need the DLC. I have non SE edition, and it works fine once its installed correctly. In any case the key is dependencies. If mods say it requires another mod, then you MUST install that mod first. Be aware that mod authors might not always be clear about what is required, sometimes you have to read the entire description to discover something is required. In addition to installing in the dependencies, the load order is the other critical aspect. You need a load order sorting tool. I use LOOT (legacy 0.64) since I have old Skyrim and Windows XP. Remove both mods, and install one, if it does not crash, install the next. This will tell you which mod has and issue, probably with you video driver or other hardware related adjustment. If you have follower mods, crashes come from incompatible skeletons, etc. In any case, add and debug one mod at a time. Its quicker.