Everything you said will work if the person using the game has enough experience editing Renpy games and/or using something like unren.bat. But in my experience someone who is new to these type of VNs (and especially if their total post numbers are relatively low) won't have a clue how to do that without having to take the time to learn how to do it first. And especially if they are already posting a "How can I see all the other endings...." question in the first place. So I intentionally avoided listing that option and gave them the short and sweet way to do it with Choice #2...(while including a sneaky "RTFM!!!" suggestion at the same time).
But both of our recommendations would work.
Hey, that was me that posted that latest question about how to see the multiple endings. What are you trying to say, haha?
I knew I could just look at the code, but I was honestly surprised that by picking what seemed like the best dialog option throughout the entire game for each dialog, even using the in-game walkthrough most of the time, I still ended up with just Sis and Connie. I thought maybe there was some key choice I missed that closed off almost all the LIs, but I guess you just have to focus on one or two at a time for each play through.
I like Sunshine Love fine, but I don't relish playing it again 6 more times, to see all the endings. Too many other games to play for that.
I know my method probably looks a bit too complex to some, but really, if you know how to copy a file using File Explorer and how to open a file using Notepad, I think its not that hard to follow my steps. And is unren.bat really harder than installing any other mod? Plus, it's fun to do it yourself rather than use a mod! (my idea of fun is different than most people)
Since you listed all the main options, I just felt like putting down an additional reference with all the manual steps here in case someone wants to use it for either this one or other games that don't have mods available.
Plus, I don't like using game specific mods (other than URM, which is great), mainly because it often messes up the save file. If the modder decides to stop developing for the game, you are screwed since the saves often won't work with the unmodded game. Or if you forget you played it with a mod or what mod you used, good luck. Plus, you sometimes have to wait a week or two after release for the mod to catch up so you can play it.
I wouldn't use the manual method for every choice, it's way too tedious. But for key game branching choices like this one, it works. Plus there are some sandbox type games where it very difficult and/or tedious to figure out by repeating events how to get to the next scene, without a mod or looking at the code, at least for me. I usually avoid sandbox games like the plague, but there are a few sandbox-lite games that I enjoy.