For soup and chili, I make the pot of food, then freeze it one of a couple of ways. I sometimes let it cool, then put it in heavy weight (name brand) freezer bags. Lay these in the freezer flat (so on a tray or something). When it's frozen, you have a flat disc that can be thawed easily. I thaw this out usually by cutting off the bag, putting it in a pot with a little water, then heating through. It is too messy for my dh, though. Which leads to the other options. I have a ton of gladware in a 1 3/4 cup size. I put soup/chili in these and freeze for single serve options. It's great for lunch. (I also do this with leftovers). OR I freeze in a couple of big gladware containers. My containers are really big--13 cups. When I freeze in these, I know that it will make enough for a meal, plus leftovers for lunch the next day. To thaw, I sometimes put in the microwave for 10 minutes at 50% power, then pop out the big ice cube into a big pot, and I finish heating on the stove. Or if I have it really together, I put the container in the fridge the night before.
For casseroles that do not matter what they look like in the end (sounds like your salmon casserole; this includes things like mac and cheese and chicken and rice for me), I freeze in ziploc bags. I do the lay flat until frozen thing again, then I'm able to stack or put on their side or whatever. Then, thaw, put in the dish, and bake through. I usually put this type of food in the freezer "uncooked." I mean, it's a casserole. Chances are a good number of the foods are already cooked. But, I wouldn't do the in the oven heating through before freezing. Save that for after thawing. Again, I thaw in either the microwave at 50% power or overnight in the fridge.
For manicotti, enchiladas, and lasagana--basically a casserole that needs to stay in a certain shape--it depends on how many dishes you have. If you have tons, then freeze in the dish, wrapped in foil and plastic wrap. You're good to go. (I wrap in foil first, cause that's what's going in the oven, but the plastic wrap helps protect my food in the freezer). If you don't have enough dishes, what I often do is line the dish with plastic wrap, then place your casserole in it, cover with plastic wrap, and then freeze until frozen solid. You can then quickly (so it doesn't thaw) take the entire casserole out of the dish, wrapped in plastic. I like a second layer in the freezer, so I'd then put it in a ziploc bag or wrap in freezer paper. For this one, when you take it out of the freezer, you put it in the original pan, thaw in the microwave or the fridge or not at all, then heat in the oven. I personally don't prebake any of the casseroles you mentioned, but you certainly could. Then, instead of baking for 1+ hours to cook through, you'd just need to reheat them in the oven or microwave.
I freeze bell peppers, but I think they get too mushy to be used for fajitas. If you don't mind the mush, then you can flash freeze veggies for fajitas. Just cut into appropriate sizes, place on a cookie sheet or tray, place in the freezer until frozen. Then you can put the individually frozen veggies in a ziploc bag until ready to use. I think if I was freezing fajita meat/tofu, I would freeze it uncooked in a marinade. Then, you'd need to thaw and grill. It would marinate as it thawed.
Good luck! I wish I had had the forethought to cook ahead when I was pregnant. It would have made those first few weeks easier.