Don't upgrade the MRCC to the Plat Travel card, you will be losing out on a lot of benefits.
The SmartEarn card offers the least value, my suggestion would be to close down the SmartEarn card.
And then apply for the Travel card, this way, you will have the perfect Trifecta.
MRCC and Plat Travel combined together will get you a lot more points!
DM me if you still have any doubts on the process or need any help!