Just wondering if there was a way to perform more detailed searches on Curseforge. I wanted to search for further only mods that relate to specific versions of Minecraft, but I can only seem to attach for the MC version number OR forge.

Pretty poor effort on their part if searches (even as relatively simple as this) are not possible.

Is there a way to search for modpacks with a specific mod? For example search for Minecraft mod packs with the origins mod included in them?

To just get straight to the point, there is no good place to browse modpacks or mods.

CurseForge's sorting is the nebulous "Popularity", the even more nebulous "Relevancy", and "Total Downloads" which are entirely unhelpful forms of sorting, seeing as they are all effectively one and the same, which is why they are 3 dominated by the same handful of modpacks. And the filters are such garbage that they are worthless, especially since you can't do any kind of advanced search (excluding categories/words, searching within version or download count ranges, etc). All of this means that an average search through CurseForge is a boring scrollfest where you finally find something interesting on page 24, inbetween "Generic Pixelmon Pack #4029" and "The Pack for My Server With 6 People".

Modrinth suffers basically the exact same problems, but is a TINY bit better on it's filters. The "Revelance", "Download Count", and "Follow Count" sorting methods are all still effectively the same from a user POV, and the lack of an advanced search still makes searching it a wade through random garbage.

The only other real place to search for them is here, but the flair system here makes it virtually impossible, seeing as every modpack and mod basically has it's own flair. And this subreddit is filled with way too many questions and the like to make just scrolling useful. Even then, the modpack and mod flairs are not just used for releases, but discussion, images, a whole host of content.

Why is this a problem? Well, you know how a lot of people say there aren't that many people willing to make modpacks? It's not true. There are loads of people out there making them. They just get buried under the high profile stuff. There are almost 2500 of them on Modrinth alone, and CurseForge has so many, that if you sort by A-Z and go to page 500, the final page, you're still in the "Ci"s. Sure, most of those, as I mentioned, are generic garbage, but there is good, more obscure stuff in there, that maybe like 6 people will play because no one can find them.
More than that, it stifles innovation in the modpack creation space. Development in modpack innovation is, quite frankly, glacial right now. Anything that can be carried over to other future packs is relatively tiny (getting rid of the giant crafting tables, for mechanical crafters, effectively the same, just with a slightly more complicated setup first) and most other innovation is so radically unique it can't be carried over without just blatantly ripping off (UniversI/O comes to mind as a super innovative pack... that can't really be easily learned from). What would help that is new ideas, instead of just the same handful of teams developing the same handful of modpack series.
It's not near as bad for mods, although a lot of the same problems emerge, just more minor, stifling smaller mods and newer creators, etc. But frankly, it's just kind of annoying when it comes to mods.

So, how do we fix it?
Well, first, just to be clear, the subreddit is never going to be a good place to browse modpacks. It's not designed for that, and that's fine. The only reason I've ever thought to resort to it is bc of how useless Modrinth's and CurseForge's search functions are.
But if Modrinth and CurseForge want to look into helping this problem, then there are a few relatively simple things they could do:
First, implement some kind of "Hot" or "Up and Coming" search sort. Only include recent releases, maybe last month or two, and then sort by either download count or download rate or some similar metric.
Second, a very basic advanced search function would be extremely useful. You could probably get away with just including a way to exclude search terms and categories, as well as ranges for download/follow count and MC versions. Modrinth, in fact, already lets you select MC versions, so they are definitely ahead in this.

If anyone else has any thoughts or ideas on this, feel free to share. This is just something that has bothered me about MC modding for genuinely several years and I wanted to talk about it and potential solutions.

EDIT: I was not aware of modpackindex, but even that leaves a lot to be desire. It lacks more user friendly sort functions, the ability to search modloaders, the ability to exclude search terms OR categories, the ability to search multiple MC versions, and more. It's certainly better, but it's still lacking a lot.

Is there a way to search for a modpack that uses two or more specific mods? For example, I'd like to find all modpacks that have both CC: Tweaked and Create.

I know that I can use CurseForge to search for the dependents of one mod, but since one mod can have dozens of dependents, it would be difficult to do this for each mod I'm interested in and then manually cross-reference them to see if there are any matches between two.