My personal opinion, is that the first service interval is a waste of money, not to get it done by a dealership!! Go around the bike with a fine tooth comb to make sure everything looks good and nothing is loose! I personally haven't ever seen anything come loose at these early stages in a bikes life. You usually do have to tighten the chain up and definitely clean and lube it by this point (600 miles) is what you must be referring to.
And there would be absolutely no problem putting the Mobil 1 oil in the bike right after 600, If you went to ten Yamaha dealerships, You would find that 8 of them use different brand oils for the same bikes! just based on their preference and how cheap they are, they usually throw some crap drum oil in it!!
I recommend using Mobil 1 4t fully synthetic, i have always used it and never had a single minor issue!
Im riding the same bike and these are the steps i have followed, This is only my opinion everyone's is different lolz