What mods are you interested in, that way I can recommend Youtubers that cover those mods or mod space/category/type. Also what version of the game? 1.12.2, 1.7.10, 1.13/1.14 (not plugging myself here with 1.13/1.14)
I thought I'd put a few Youtubers and then a few simple searches to cover the general things you might be looking for. Otherwise I'd check the Curseforge mod page mostly to see what stands out and then go for the videos if you want more in-depth on how to use them or what the mods offer in action. But that's just me I guess, it's up to you really.
Direwolf20 is a must for Tech or Magics mods of the mainstream kind or the odd mod here and there you come across but don't hear about much or have videos covering updates of,
I don't usually stick with Youtubers for mods anymore due to covering mods I like/find so I can't recommend many unfortunately, that and I stuck with Direwolf20 a lot and searched for mods from Youtubers for that video/mod spotlight. Or I learned it from scratch instead. I'd have to go back over the mods I've played to find those Youtubers.
While there are many out there big or small Youtubers, I'd say look for the mods you want and find the Youtubers from there. It's mostly how I do, or if the mod isn't covered I do videos on it after I learn it but that's if your into niche/few downloaded mods like me and have played most of the big ones most will recommend, for me I have to learn it when they really don't cover them or few do at least depending on if it's acknowledged or not (Videos that don't cover the mods or after covered by few Youtubers or the Creators of the Mods themselves I mean).
The Meaning of Life, the Universe, and Everything.
If you look up the words "<pack name> mod spotlight" you will get exactly what you are looking for.
I am incredibly critical of YouTubers and have really only found 2 that I like, DireWolf and CheersKevin. These 2 YTers get to the point without a lot of extraneous information and don't have severely annoying voices.
If I may offer some advice for learning how to play modded... pick 1 mod and learn it. Don't worry about anything else until you have a firm grasp of THAT mod. The very first mod I ALWAYS recommend learning is Tinker's Construct. It is simple, practical, and provides fantastic tools and ore doubling. From there, learn something like Immersive Engineering. IE is a major step forward in modded knowledge, but it includes everything you could EVER want: ore doubling, energy generation, item and RF transport, automated mining and soooooo much more. The other mod I strongly recommend is Actually Additions. AA has the best mining tool (Actually Additions Drill) hands down. It also has automated ore generation (lens of the miner) and wireless item/RF transmission (phantom interfaces), and so much more. If a magic theme is more your thing than the tech side, start with Botania and then move to Astral Sorcery, Blood Magic, and Thaumcraft. IMO, magic mods are far harder to understand than tech mods.