You're off to a good start but balance out your applications, annual fees, minimum spending and benefits so you don't overextend yourself in any one, or more, direction. Unless you have a long credit history with solid income it's wise to pace yourself. Applying for too much credit makes you look like a risk to banks and if you get labeled as a churner they can deny you future cards or bonuses.

The Amex 100k MR offer for the Platinum is quite good and you can recover much of the annual fee each year but there is also some overlap with the CSR. If you travel a lot that can be a good thing as CSR's PP membership includes restaurants while Amex does not but does come with lounges that Chase does not offer. General downside to the Amex Plat is the limited earning potential. Unless you book a lot of airfare or hotels via Amex Travel/FHR the earnings is limited which is why many people pair it with the Amex Gold for 4x earning on dining & grocery.

For Chase, if you have the ability, look into the Chase Ink cards. The CIP has the 80k UR offer for a $95 AF with some earning potential but there is also the CIU which has a nice 50k UR offer with no AF and 1.5UR on all spending. Ink cards are bound by 5/24 but do not count towards 5/24 so they give you some time to have other cards drop off your 2 year application period.