Skill Assessment for EOI (189/190/491)

I graduated as an Electrical Engineer (Major in Electronics) from an Washington accredited university. I pivoted towards Data & AI and been working as a Data Engineering professionally for 4 years now. What do I use for skill assessment? I am guessing its ACS. Second question is, do I need to get my skill assessment before submitting EOI or can I do it if/after i get an invitation? It costs $1450 to get skills assessment from ACS and its a big amount, I want to be sure it isn't wasted if i don't get an invitation.