I'm seeing the option to hide the symbols on both my iPhone and on the watch itself:
That said, I prefer the way another app (Heart Watch) presents the data. Here they are, side-by-side (the lower left complications). Heart Analyzer is on the left, and Heart Watch is on the right (click to enlarge):
Heart Analyzer's low/high text is white, and too large (in my opinion). Heart Watch uses a smaller font, and differentiates the numbers by color, which I prefer. I also prefer Heart Watch's color palette, because it saves the RED section until the very end of the circle (right, bottom) which makes more sense to me (Heart Analyzer on the other hand transitions to red
far too quickly, which sort of implies that a pulse rate of 76 - as in the screenshot - is in the RED zone, which it most certainly is not). That said, the data presented in the apps themselves is far better in Heart Analyzer, in my opinion (it shows a chart graphic, whereas Heart Watch simply shows a speedometer-esque graphic showing current pulse).
In my case, I actually review my health data on my phone (never on my watch) so I tend to just go for apps with complications I like, visually. For me, that's Heart Watch (rather than Heart Analyzer). YMMV.