The Fw 190A-3/U1 had an ETC 500 bomb rack & the MG FF canon were removed.
The 190A-3/U3 had an ETC 250 fuselage rack, & some had additional SC 50 racks on the wing.
The a-4 verson had a revised tail top (as in A-8, F-8, etc.)
The A-4 also had wheel covers that were hinged on the fuselage.
Hope this helps.