I think you need to be guided by the medics managing your care, as there will be a balance for you that's good for your diabetes and your kidneys. It will perhaps depend on what is causing the kidney deterioration in the first place. If it's because of the diabetes, it might be that prioritising on improving that may reap benefits to your kidneys, but only your medics and you will know what your individual circumstances are.
My husband has stage 4 CKD and is being prepped for dialysis, his has been caused by major organ failure 10 years ago and the damage done at that time, so there's nothing he can do lifestyle-wise to improve his function, other than drinking gob-loads. But the advice he has had has been to eat a healthy well balanced diet, ensuring that he does eat enough carbs - that does seem to be the one piece of conflicting advice between kidney issues and diabetes.
We discussed the idea that protein should be lowered and his current nephrologist said they weren't worried about that these days, they always used to restrict protein, especially on dialysis, but found that whilst on paper, some numbers improved, the patients didn't in themselves - long term they ended up malnourished and healed slowly. They now believe that remaining healthy, with good food and exercise, is the best approach to long term well-being and outcomes. We even asked if he should restrict foods like oranges as you read this often and he eats a lot of them, but he just shrugged and said at was a bit of an old wives tale too these days - they prefer a good healthy balance.
Probably choosing the right carbs in terms of quality and quantity can probably benefit both for your health issues, but your medics will be the ones to guide you.
My husband is under the care of a multi-disciplinary team and they all talk and E-mail each other even when he's in consultations, so they look after him as a team, so hopefully your docs will work in a similar way, to ensure that all of your interests are served best. We've now cut the GP out of the equation, as they seem to be perpetually 12 months behind the consultants and never seem to actually read their long and detailed letters.
I wish you luck - your medics are the ones to advise you on what balance will be best to manage both conditions.