I wrote these chord progressions to help students with their Rockschool Improvisation (based on the 2012-2018 syllabus) practicing. I would also highly recommend getting their companion guides, which have official practice exercsies. My exercises are just as an add on to these practice examples, so you can get plenty of practice in (they are not endorsed by rockschool in any way).
You are free to play the chords as open chords or as barre chords – whatever you want. Barre chords would be grade 3-4 level, and open chords would be grade 1-2 level. For anyone not doing an exam, what you do need to do is improvise your own rhythms to make things interesting and to get the most out of the sheet. If there is 1 chord per bar, it will need to last for 4 beats, and if there are 2 chords per bar, you need to play those for 2 beats each.
For the actual rockschool exam though, you only need to follow the same rhythm for each Improvisation & Interpretation exercise, which can be found in the example in the grade book. In RGT, you would be required to develop your own rhythms.
You could extend these exercises into playing them in different styles, tempos, and time signatures (although all the Rockschool ones are in 4/4).
Whilst these chord progressions exercises were written for guitar, you could definitely use these for ukulele chord practice.
Related Post: A minor Chord Progressions Exercises – Grade 3 →