It's funny but we are the opposite - l like a little spiciness to my peppers and the wife dislikes spicy. So we compromise and I'll often make poppers using both jalapeno peppers and the little cocktail bell peppers.
Everyone has a different sensitivity to
capsaicin, the active component in hot peppers. Even sweet bell peppers produce minute amounts of it, it's too low to detect. For example, my mother can not eat raw bell peppers as they will give bad indigestion and can only eat red bell peppers in small quantities when they are thoroughly cooked. I, on the other hand, can eat both raw and cooked peppers alike. However, I have definitely become more sensitive to capsaicin with age - when I was younger I could eat spicy foods with little external side effect; nowadays, if I eat any spicy peppers, I sweat profusely from my head (I "get wet" as the pepperheads like to say...). That development occurred over the last 10 years I would say.
When cooking with spicy peppers, I don't ever use the high heat peppers like habanero's (and certainly not the silly ultra hot peppers like the ghost peppers or Carolina Reapers....that just dumb!). I feel those peppers are best left as a garnish to a dish or, in minute quantities served on the side for those that want to add a little extra heat. Adding peppers like that to any dish thoroughly ruins the food in my opinion because the intense heat and discomfort it causes overwhelms any enjoyable aspect to eating. Leave those peppers for making hot sauce & pepper spray!
My go-to peppers are - Serrano, Jalepeno, Poblano and Bells (those are in order of descending heat). To adjust the heat of the dish, I find that I will usually cut open the peppers and strip out all the seed and white pith/ribbing as that is where 99% of the capsaicin resides. Fully cleaned out peppers will be a lot less hot and then you add back in a regular pepper to increase the heat. Roasting the peppers also helps to degrade the remaining capsaicin and leaves behind a mildly spicy and smokey flavor. The best way to roast a pepper is on the grille; ovens work too but I feel they take a lot longer and, in the summer, just heats up the house. Simply rub the pepper with a bit of vegetable oil and roast the peppers until the skins blister and turn black. Then seal them in a glass bowl and let them cool all the way down to room temperature. The sealing is important because it keeps the steam in which helps to separate the charred skin from the flesh. Then just clean out the pepper insides. Some people clean them out under running water which helps to remove all the seeds and ribbing. I like to clean them out over strainer and bowl to capture the juices that come off the peppers when you clean them out (the strainers captures all the charred skins, seeds and ribbing). The juice can be added back to whatever dish you're making with the peppers (great addition to fresh salsa mixes). Whatever you do, roasting the peppers helps a lot in revealing the flavor and reducing the heat.
When I make poppers, I use cheese as the main ingredient of the filling. I always mixed whipped cream cheese with shredded cheese (and add bacon!!) and stuff the peppers with that. The oils and milk in the cheese help to reduce absorption of the capsaicin by your mouth and so it makes them very enjoyable as a side dish or snack. When I make my chili verde, I use roasted peppers and I slow cook it. Slow cooking helps to also degrade any capsaicin. When I make fresh salsa verde, I use roasted tomatillos and roasted peppers with olive oil, lime juice, a little bit of white sugar, salt and roasted garlic. The heat is easy to adjust by simply adding in some fresh jalapeno while it's blending. I get lots of compliments on my fresh green chili salsa.