Noob question: Does my kit assembly matter? Hi,

I've been painting AoS minis for a few months but I've never actually played (although I hope to one day when my local game store re-opens inside).  I've been picking my kit based on what I think looks cool and I suddenly got worried that these choices have actual consequences.  If my guy is supposed to wield a sword but I build him with an axe (or another kit variation) does it matter?  Is it only table legal if the assembly matches the stats?

Thanks.