I have Strava premium which I use on an iPhone 6. I pair it with a Wahoo Tickr HRM (Heart Rate Monitor) which supports both ANT+ and Bluetooth, so it has the flexibility to be paired with a cycle computer, phone, or laptop. I don't tend to use the HRM more when I'm on Zwift than out on the road with Strava, but I am familiar with Strava Premium and the heart rate based metrics it can provide.
At the end of the day, both a cycle computer (I'm thinking Garmin/Wahoo Elemnt) and Strava Premium will collect the same data (i.e the output from the sensors). In your case this would be a recorded heart rate, position/route, and speed. It's really what you do with that data that's important, and I think that is what S-Express is getting at.
Strava will give you a free one month trial of Premium, so I'd suggest getting a HRM (the Wahoo Tickr is about £40) then starting a trial to see if you find it useful.
One feature of Strava Premium when you use a HRM is fitness/freshness scores. As you train you will see your fitness score increase, and your freshness score decrease (because your body is getting tired). It is using the data from your sensors to give you some meaningful numbers that can show you in an easy to understand way how fit you are and how fresh you are. You'll feel these differences too, but "feel" can be deceptive!
If you want to take the training more seriously you will need a training plan - there are free plans available online which you could follow. Just going out and riding will improve your fitness and will almost certainly improve your lap times around the park, but if you use a training plan you will see bigger improvements. British Cycling have some training plans which you might find useful.
Here is a link about Strava's "Suffer Score" and fitness/freshness:
https://support.strava.com/hc/en-us/articles/216917077-Suffer-Score-Premium-
https://support.strava.com/hc/en-us/articles/216918477-Fitness-and-Freshness-Premium-
I use some of the training plans on Zwift to train on my turbo which is good fun, and I can see the results in my improved FTP (Watts) and ability to ride harder for longer on the road. In your case, you could use a British Cycling training plan (maybe a TT one) with your HRM and see the improvements in your lap time around the park.