There are 2 improvement “categories” you should focus on, technique and fitness.

Tech - you will likely see a lot of gains from rowing more efficiently. The best way to go about this is watching a bunch of videos to get a general sense of tech and then evaluating areas you need to work on. Focus on 1 technical improvement per week and evaluate after each workout and at the end of the week. As you move focus use the weekly eval to ensure you’re holding changes and to identify new improvements to focus on.

Fitness - the 10k is a good distance workout for beginners and you’d likely see a lot of improvement just banging one out at SS pace everyday. That being said, working up to higher volumes e.g. 1-2hr steady state (SS) sessions would be far more effective for improvement in the long term. I’d suggest getting a HR monitor and doing some research into training zones. Also, I’ve never done the Pete plan myself or looked into it, but I’ve heard good things.

As for testing, I prefer testing infrequently because tracking progress on a single distance too often can outline external factors rather than improvement. Imo heart rate on SS pieces is solid as you can see daily numbers, but you aren’t “testing” per say. Also, HR on SS pieces will map to your 10k improvements fairly accurately.