As the title suggests, I'm new to AoS and am not sure what the pros/cons of assembling the standards and drummers for each five man squadron are and if it's worth doing it for all of the three squads. I know what the abilities for the drums and banners do, but do I sacrifice attacks for not having them wield regular weapons? Everything I know I've learned from battlereports and playing 40k, I don't have access to the core rules for AoS which would probably provide a quick answer to this question. So instead I ask you fine Lustrians.
Welcome to Lustria Online. Great question. No, you don't sacrifice any attacks. It is in the core rules under unit command. All units with Drums, banners, ect are assumed to have their standard weapons even when not modeled with one. However, AoS in tournaments is Wysiwyg. That means if a unit can't have two banners then you cant have two modeled with banners in a 10 man unit or larger. So, if you only want to run them as 5 then just make three units of 5 with full command! Which is what I recommend to start with. Later you can buy additional units to fill out the unit sizes and build them without their command if you decide to expand your Saurus Guard Collection. Ps. here is a link to the free Core Rules pdf provided by Games Workshop. See page 13. Section title Command Models.
If you're planning to play Seraphon long term, and if you're a new player, I highly recommend reading some of the posts on tactics on this website. The people here and their opinions have been a nearly invaluable tool to me, and a goodly sized chunk of my usual tactical doctrine has come from here, with some alterations for my local meta of course.