What do you use when wearing your mechanical watch?

Yes, I have a Vivosmart 3 for days when I wear a mechanical watch (not that many,  but sometimes the occasion requires something a notch smarter)

Gave up wearing a mechanical watch years ago when I started carrying a cell phone - I don't like mono-tasking tech.

The titanium finish F6 looks good with a business suit.

Here's a photo of someone wearing the 47mm Fenix 6 Titanium with a leather band under a business suit, next to a stock image of the 51mm Solar Ti version.

If that's not blingy enough, there's the Fenix Chronos or MARQ line. Here's the Titanium Chronos next to the MARQ Aviator:

The MARQ is current tech. The Chronos is based on the old Fenix 3HR but still tracks more biometrics than the "zero" you'd get from a dumb-watch. Neither would be embarrassed next to an Omega Speedmaster.

If all you want is a step count while wearing something else, get a Vivofit 3 and put it in the optional belt clip.

You won't get all the stats, but you could also just have the Garmin in your pocket when you are wearing the other watch.

That wouldn’t give you HR and then you wouldn’t get BB, is that right? 

Vivofit doesn't have HR. Chronos has HR but not the latest HR sensor so no 1-second sample rate, no HRV stress, no Body Battery. MARQ has everything.

I have same dilemma with 2 apple watches and currently 3 Garmins.  I also have 45 "regular" watches from G-shocks to automatics to quartz.  I sometimes wear a regular watch during the day and put a smart watch back on at night for sleep tracking, SP02 measurement, etc.  I've sold some regular watches and have more to sell. My daily tracking and stats don't vary much, so I've resigned myself to giving up that data. Main goal for me is to track activities and their contribution to my allowed calorie intake.  

45 watches? 

Most of 'em:

Given the content of the display case, I see a Garmin Instinct (or six) in your future! 

Had one. Liked it. Sold it along with F3, F5, F5+ to get the F6.