Welcome to PPRuNe Neb,
Though I do not have a "medically qualified" answer to your question, I can offer the following thoughts: Go to see a medical examiner, and ask their opinion. Understand the distinction that the medical examiner is delegated by TC to report their examination results, but it is TC [their doctor] who issues (or not) a medical. The fact that the examiner advises or passes you does not mean that you get a medical. The medical examiner will be your friend, but doesn't hold the keys. TC holds the keys, but are neutral at best. They err to the side of being cautious, and my experience with them during a bump in my medical was non ideal. Perseverance (and actually being medically qualified) got me through, not TC help. So enter the process knowing that it's not a certain outcome until TC agrees, and you won't know that until your examination is submitted.
Consider what you'll use your license for. Generally, I'd advise an applicant toward a "higher" medical, to allow for license expansion, but I believe that having a non smooth Cat 3 medical can make the Cat 4 more difficult to get. So seek your medical examiner's advice on that. If you plan to simply use the RPP privileges, and not expand your goals toward PPL, seeking only a Cat 4 in the simple path is "safer" for you. If getting the medical you seek is difficult, there is a path for you to petition TC, so don't give up. As you're otherwise healthy, that is a great stepping stone toward getting a medical. I do know that TC considers your health and lifestyle in the bigger picture, so evidence of non smoking, non drinking, good body condition, and regular exercise will certainly be noticed and help you. In my first response to being summoned by the TC doctor (looking into my medical health following being in an accident) I had ridden my bike to the TC office, and had it folded with me in the lobby - I know that he noticed that with [good] surprise, and that had ultimately worked in my favour later.
Get your medical situation sorted before you invest "much" in training.
Good luck!