obsiid

I'll go from what I deem most important to least.
Also, I'm playing on 1.16.1, which should be the latest version on curseforge. If you play on FTB launcher you will likely have a newer version
Performance! I used to play this on a really bad computer. There are a couple of things that will send you back to the title screen but overall it runs well.

There are quests in this pack, but to properly play the pack you should know about lots of mods. The end goal of the pack can be thought of as Infinity Ingots but there is a special item called "Balanced Clay" which I would say is the true end goal. It's not in the quest book on the version I played so I reckon I'll mention it here.

As for some things you may dislike, good luck trying to beat the pack without chickens, emc, draconic evolution, or AE2. You will have to build a mob farm but you can hold off for quite a while.

Playtime!
My first playthrough years ago lasted over 2 weeks of playtime, I got a full set of infinity armor without much use of EMC. It was my first ever mod pack, so I except a complete noob to take about this long if they have never touched modded minecraft and don't have much of a grasp on it.
My playthrough with a friend recently lasted only 50 hours, and we both spent a lot of time AFK so I can't give a good estimate. This is the speed you'll go if you know what you are doing.
I reckon now that I know the actual progression route, I might be able to beat it in one sitting if I focus.

TIPS!
Make a time in a bottle asap for chickens, I have more but spoilers doesn't work

While the default settings are very unbalanced and honestly hurt a lot of things more than they help, the mod is SO customizable through configs and datapacks that you can basically make it anything you want.
By default:
-Sugarcane grows to world height, and cactus grow 5 blocks tall.
-New enchanting system, which is very great and I don't need to make changes to ever.
-Spawners can be upgraded, and in the config you can change the item required to upgrade different stats, by default it's pretty easy to make it ridiculous. You can also change the level of Silk Touch required to mine a spawner and keep it.

And the systems which I always have to change extensively, Affixes and gems
By default, gems spawn from enemies at a decently high rate, they spawn in structures and they can be created by the player using other gems. Gems aren't very strong generally and are very chance based.

An affix is another way to refer to a stat, affix gear from my understanding just means "gear with a stat boost" For example, an iron sword with increased crit damage, or a shield with increased movement speed. Anyone want moon gravity pants?
Generally, these are weak on low tier equipment, which can be gained from random zombies, and in overworld chests.
High tier affix equipment can be gotten plentifully in the End, high tier affix gear is ridiculously powerful and needs to be purposely tweaked if not fully removed most of the time. If you don't care about balance, then you shouldn't worry about this part, go explore the end!
You can "salvage" the gear and gain "affix materials" which allow you to apply affixes to any gear, not just vanilla! You too can finally have your cotton candy affix sword! If you don't have any mods that add gear, that's okay, you can use it to reroll your affixes instead! It's basically an enchanting table that works on previously affixed gear.

As I said before, you can change (almost) everything in the mod! Don't like the enchanting? Goodbye enchanting! Only want the sugarcane to grow a little? Sure! Perhaps you wish an affix to deal 100 thousand damage? I don't see why you would, but you can!
I generally remove ALL natural ways to get affix gear, and allow you to gain the crafting materials yourself through a complex crafting tree using the KubeJS mod. This is generally beyond a normal player, I suggest disabling boss spawns so that the equipment is rarer.