Welcome to SMBX.org, enjoy your time here in the community. SMBX 1.3.0.1 is just bugfixes n' stuff, also adds a default episode iirc. Just make sure you read and follow the forum rules, and I think you'll love it here.
Hello @Mattheww00 and Welcome to the Forums. I am @bossedit8 who makes Levels, Episodes and even Videos based on SMBX and sometimes Mario Builder, Touhou, ZSNES Emulators and rarely more.
Have a very nice time and please follow the Forum Rules.