The Rogue Wolf said:
I know you've had a handful of answers already but as a Skyrim vet with ~1000 hours (Recently around ~80 on the special edition) I think I'd weigh in.
1. Dawnguard DLC gives access to crossbows. Will I be able to buy them anywhere or do I have to play the DLC to get my hands on them?
I don't think offhand that they show up in leveled loot lists, however Sorene sells them. She also sells new bolts and even the dwarven variants which are a LOT stronger if you do her few radiant quests that involve delving into dwarven ruins to nab some schematics. It's about 4 quests in total and it's worth doing if you want to take the crossbow as a serious main weapon. Without mods, the Advanced Dwarven Crossbow is a mighty fine piece of equipment.
2. I've checked the perks in Speech tree and they don't seem to be too interesting. Am I correct in thinking that putting points in them is a waste of points? Or am I wrong? And if I am, then why?
I've been running a perk overhaul for a while now so it's been some time since I've seen the vanilla perks but I recall only being a couple of relevant perks: One that allows you to sell any item to any merchant which saves a LOT of general foot traffic and running around town. Another allows you to invest in shops that increase their money pool which helps in the long run.
Speech is one of those you can't really powerlevel either, you just kind of have to let it build up over time and toss it a perk as you see fit.
3. I really like spells in Destruction school, but I remember that someone somewhere mentioned that in this game Destruction spells are severely underpowered and it is better to go with Conjuration? How true is/was it for you?
Without mods, most magic is underpowered. There's a few neat utilities like the muffle spell, maybe some wards if enemy mages are giving you trouble (I remember ice mages being the bane of my existence pre-mods, back when I played it on the Xbox).
Conjuration is not a bad choice, but the levels of all the summons are static. The Dremora Lord (Expert level, 75+) can be useful at times as it wields a fire-enchanted Daedric 2hander which can wreck shop but it only wields 350 or so hitpoints and doesn't level with you to my knowledge.
With a simple mod or two, Destruction magic can get increased damage for every point of Destruction skill you have, so it will level with you all the way. However I do not know what platform you're playing on.
4. I am thinking about finishing "Civil War" questline first and then doing other stuff. Is there a recommended minimum level that I need to have in order to successfully finish this questline? Or I can simply jump into it?
No minimum level. Most enemies are "guard" type NPCs and generally speaking, level with you. Regardless, at a certain point (30-35+ perhaps) you'll be mowing through the enemies that it might not be as fun. I recommend increasing the difficulty to they take around 3 hits to kill, then it will feel like a real battle.
I did this with my Knight-Paladin type archetype, did the quest in her 20's on Adept difficulty. The final battle was intense and hilariously fun, especially when a Frost Dragon came into the fray. Night time, frost dragon, civil war with constantly respawning enemies and a couple of chokepoints they held for several minutes. It's one of my fondest memories of the game; But unfortunately the questline itself is badly written and implemented with very weak rewards.
Once again, some of this is mitigated with mods. "Immersive patrols" comes to mind, where sometimes I run into full-on skirmishes, 20 v 20 battles that I hopped in on.
5. In this game you can become either werewolf or a vampire. Is it worth it? If yes, then which one is better? Also, if I become a vampire, will I be able to finish Dawnguard questline on human side?
No. The werewolf is easier to deal with as the game doesn't 'force' you into werewolf form, so it's useful to just take the 100% immunity to disease and run with it. The form is fun to play with but (Again, without mods) it's hardly worth running around in wolf form.
Vanilla vamps have it rough. The lord form is neat but being a vampire in common gameplay is irritating as it cuts off all regen in sunlight which makes running around a chore. The Lord perks also do not apply when out of form so you're mostly stuck with a handful of negligible spells, most of which you can get from common magic tomes to begin with. The vanilla Vampire Drain spell is hilariously weak.
I will say that they ARE a bit more playable with Dawnguard DLC, as you get a whole vampire coven to play with and radiant quests that cater specifically to vampires. They also have their own vendors who wander around most hours to help mitigate the vendor run. I typically use Riften for a loot drop as they have like ~5 vendors in the same area, but it's annoying to travel there and then wait til daytime and then run out of stamina immediately with no regen.
(Again, I run "Better Vampires" which gives a whole rank system and a dozen or more new abilities to play with).