Training plan question - trading RPE zones for HR zones

I'm training for my first sprint triathlon, which is happening in one month. I've been following this training plan - http://www.triathlete.com/2017/02/training/8-week-sprint-triathlon-...

I chose that plan because it was the right length (I had two months to prepare), and I liked the amount of detail it provided (even though I would like even more detail).

I'm not a total beginner in endurance sports. I trained for and competed in a 10K running race earlier this year, and I've done other running races in the past. For my recent 10K, I followed a basic Hal Higdon training plan, and I only ran and did cycling to cross train (no swimming).

I've spent most of the first month of my current training plan focusing on swimming, as I'm a total newb. I'm making progress with my forward crawl, but I have a long way to go. I've also been doing most of the runs and rides in the training plan, however, since I wasn't a beginner, I did somewhat longer and harder workouts.

This week I decided to follow my training plan more closely. However, it bases everything off of RPE. RPE is okay for what it is, but I'm a bigger fan of more exact training metrics. So, instead of following this training plan to the letter, I've decided to trade the RPE zones in the plan with heart rate zones for the bike, and power zones for the run (I use a Stryd running power meter, but I don't have a power meter on my bike).

Is this a workable plan for my final month? Will the RPE zones in the bike workouts translate to HR zones? Do I perhaps need to up them a bit? For context, I've been riding my road bike pretty consistently for around six months.

To get my bike HR zones figured out, I tested them this morning on a stationary bike at the gym using the test in this article - http://www.bicycling.com/training/fitness/how-to-train-with-a-heart...

I'm less concerned about the power zones translating to the RPE zones in the plan. I'm a much more experienced runner, so I feel more confident in my ability there. For my swim training, the RPE zones are good enough for my needs.

The training zones for the bike are my main concern.

Thanks!