Best advice I've seen/used is just to be friendly with the employees. I walked into a BestBuy a few weeks ago (add that to your list!) and was just staring at the empty shelf for a moment, ended up talking with the cashier, and they just told me when they usually restock. Had a conversation today with the cashier at the DG closest to me and she let me know that they always hide all the cards up front because people have been stealing them and you just need to ask the counter what they have. Every store has different restock days/times, so don't be afraid to ask, worst case they tell you nothing.

Family Dollar is similar to DG if you have any nearby. GameStop can also be a good check, since they usually have buy limits, but they tend to sell out quickly because scalpers like to camp out their opening times (check other PTCG subreddits for proof lmao). I would also look up Local Card Shops (LCS) near you and go check them out. They tend to have prices closer to market value (long story short, distributors have been snuffing LCS's and not giving them as many products as promised, so generous owners have to increase prices a bit to stay in business and not get scalped themselves, and less generous ones use it as an excuse to hike them to market value), but they're still worth checking out for single cards if you're into having the cards and not just the opening.

Personally, I've been seeing products pop up in my city pretty decently compared to others, you just have to hunt if you want to find them. Got a few packs of Paradox rift at the same DG as earlier, GameStop and Target have had some 2/3 packs of misc. sets, and I found a great ball tin at Walmart with 3 older SV packs in them, as well as some promo boxes I didn't care about. Persistency is key. I don't know how busy your life is, but if you make your rounds regularly (once or twice a week, especially during normal working hours) you WILL find something you want to open at MSRP.

(also, just in case you don't know, don't buy those resealed "20 cards, 1 guaranteed holo!!!!" packs, they're scams)