Ok so I have all the conjure spells like conjure ash guardian and ash spawn and boneman dremora lord etc so I usually play as a archer/assassin and I was wondering what conjuration spells were useful against which classes like I know dremora lords use a daedric greatsword with fire enchantment so it is good for a lot but what are the strengths and weaknesses of the other conjuration spells like ash spawn or seeker etc
For the general strength of the creature you can kind of go by the skill level of the spell (adept, master etc), but with the elemental potency perk Atronachs will be a bit stronger (but not as strong as the Dremora). The Frost Atronach can be handy (or the opposite) for blocking door ways but the Ash Guardian is more tanky, the Dremora is handy for just killing stuff. A Flame Atronach makes a good turret or a Seeker, they do less damage but it's attack isn't elemental and a drain spell so possibly keeping them around longer.
In general go by the level the spell and any element they might use and be resistant to, fire does a bit extra damage so good in general. Frost slows movement and drains stamina so good against melee enemies, Lightning drains magic so good against magic users (and dragons as their resistant to the other two).
Level and element. The Boneman spell is only apprentice level it's a weak skeleton that uses a bow, the Mistman is adept level a bit stronger and uses ice magic. The Wrathman spell is expert and similar to the Dremora.