Playtesting Combos does matter, because there's some glitches you wouldn't know about if you just write them out without trying them. For instance, Wall of Lightning glitches Impact so it doesn't stagger, so one might write a Storm Mage suggesting that combo without testing it, because it requires Expert level spells, and a lot of Magicka (Or enchanting to Free Destruction) to pull off.
Also, if you don't start off, and work the skills up without grinding, it can sometimes reach points in the mid game where you're temporarily too weak to survive, because you went up an NPC tier, but didn't compensate with the skills/equipment.
And finally, unless you know the calculations, you might work up a few skills on paper, then not realize that while you have 30 perk points, you aren't level 31 because you don't have enough experience with those few skills at level 100. Especially if you believe people who say "Skill bonuses don't matter," an Altmer may be able to get 30 perks with a certain skill set, while a Nord wouldn't.
So yeah, you can Assume a build will work, or you can playtest it before posting.
Playtesting Combos does matter, because there's some glitches you wouldn't know about if you just write them out without trying them. For instance, Wall of Lightning glitches Impact so it doesn't stagger, so one might write a Storm Mage suggesting that combo without testing it, because it requires Expert level spells, and a lot of Magicka (Or enchanting to Free Destruction) to pull off.
Also, if you don't start off, and work the skills up without grinding, it can sometimes reach points in the mid game where you're temporarily too weak to survive, because you went up an NPC tier, but didn't compensate with the skills/equipment.
And finally, unless you know the calculations, you might work up a few skills on paper, then not realize that while you have 30 perk points, you aren't level 31 because you don't have enough experience with those few skills at level 100. Especially if you believe people who say "Skill bonuses don't matter," an Altmer may be able to get 30 perks with a certain skill set, while a Nord wouldn't.
So yeah, you can Assume a build will work, or you can playtest it before posting.