Would you stop an ACE inhibitor/ARB or instead initiate a potassium binder to manage hyperkalemia in a patient with proteinuric CKD stage 5 who is on an ACEi/ARB?  

This depends on where in CKD 5 the patient is, to some extent. Would also make sure to modify diet if possible and make sure on an appropriate dose of a loop diuretic. If very close to starting dialysis or getting a txp, I might reduce dose or stop, especially if a K-binder is expensive for the pati...

Let’s assume that your patient is on a low K diet, on a loop diuretic and with no acidosis. I wouldn’t still stop the ACEi. 

This is a situation where 'one size does not fit all "and has to be approached per individual patient risk of progression of renal failure and life-threatening hyperkalemia with limited reward of halting /slowing progression.

ACE-I’s and ARB’s have been shown to slow the progression of CKD, especially in patients with proteinuria. If potassium elevation is considered to be a problem, potassium binders are an excellent treatment to prevent high potassium levels and continue patients on drugs that act on the RA...

I would always keep the inhibition of the RAAS to continue in a patient with CKD and proteinuria. Lowering K with a K binder is a safe and effective way to maintain the renal protection offered by either an ACE-I or an ARB without causing hyperkalemia complicating the continuing inhibition of the RA...