Edge 130 or Edge 520+ with existing fenix 5S

If you link the 520+ to the Fenix it'll be extended display mode and therefore as dumb as the 130. If I were going to choose I'd go with the 130 as an extended display as the screen is much clearer than the 520.
You can, however, use a Fenix and Edge at the same time and then just delete one activity rather than saving it. Or you can save both activities and delete one from Connect - Strava will only sync one activity if the times match so no issues there.
Finally, and the most recommended of all, would be record on the Edge. If you want optical HR you can broadcast this from the Fenix to the Edge. When you save on the Edge, the activity will sync down to your Fenix and give you the correct recovery stats as if you'd done it on the watch. This is called True up and is a recently added feature so you'll need to be up to date on firmwares. Hope that helps :)

The cheapest option would be just to get a handlebar mount for your watch. You would need a chest strap to monitor HR, but wrist-based OHR is problematic with outdoor cycling anyway, due to vibration from the handlebars.

520+ is the more capable unit, but seems like overkill if you are just going to use it as an Extended Display, and not use the mapping capabilities.

If you have the watch and Edge syncing to different Garmin accounts, there is no need to delete duplicate activities, but the data would still be available if you ever needed to re-import it.

Finally, and the most recommended of all, would be record on the Edge. If you want optical HR you can broadcast this from the Fenix to the Edge. When you save on the Edge, the activity will sync down to your Fenix and give you the correct recovery stats as if you'd done it on the watch. This is called True up and is a recently added feature so you'll need to be up to date on firmwares. Hope that helps :)

This sounds like the best of all worlds since I do (perhaps less frequently) want to use the Nav functions for more adventurous rides I'm planning next spring! I hadn't considered using the Edge to record, I take it that the HR component of the fenix can be attached to the Edge in the same way I've attached speed and cadence to my fenix?

Thank you for sharing your ideas and tips. I can understand the cost effective nature of the watch-mounts, but i really would prefer to keep the watch on my wrist - I'm a sucker for the "out front" mounts too!

Correct. On the Fenix go to the menu, Settings, Sensors & Accessories, Wrist Heart Rate and you'll see Broadcast Heart Rate which you can choose to broadcast right now until you stop it. You also have a setting for Broadcast During Activity so that you can record on the watch and transmit the HR data. This will always transmit HR when recording so it's more convenient. Both options broadcast as if they were an Ant+ HR strap so the Edge won't know the difference. Also, because Ant+ is a broadcast you can connect all sensors to both devices if you wish - Bluetooth sensors mostly don't let you do this.
If you like, you can also add Broadcast Heart Rate to controls in Settings, Controls. This puts it in the quick access menu when you press and hold the top left button :)

The 1030 has a relatively new feature that I haven't tried yet that will show the data from your 5S. This is really useful in triathlons when the user is really more concerned with recording all the data on the watch, but wants a bike computer for viewing. I doubt that I will use it as I prefer to just watch my data from my bike computer when I'm racing.

I have and love my 520, but bought a 1030 for the map feature and longer battery life as I was riding long long rides in France a month ago. However the 520 actually follows a course better than the 1030 if you don't have the map (I didn't have the Europe maps). The 520 is so inexpensive today, I'd go that way if I were you.

An update... I bought a standard Edge 520 because they had a really good deal on Chain Reaction. I’ve set it all up and added the Wrist HR sensor. While in broadcast mode however, it only broadcasts if I am on a HR watch face on my fenix, or when I’ve started an activity on my fenix 5S. I’d have hoped that I could leave the watch on the default watch face and broadcast HR when the Edge was recording, but it won’t seem to do this... Is this something I’ll have to put up with, or am I doing something wrong?

Interestingly, when in manual broadcast mode, the HR isn’t broadcasted to a recording Edge activity?!

I wonder... could it be that it isn’t broadcasting because my HR is in a resting state, and that it might start auto-broadcasting when I’m elevating during riding?

The sampling of the wrist OHR is far less frequent when in watch mode, than during an activity, so the quality of the data will be lower. If you want wrist OHR for your ride, I'd recommend recording the activity natively on the F5S, and using the Extended Display mode on the 520 to view the data while riding.

Alternatively, you could start a generic Cardio activity on the watch (with it set to broadcast), then Discard (rather than saving) at the end. This would give you the benefit of the more frequent sampling (and therefore better quality data), without the power drain of running the watch GPS.

If you link the 520+ to the Fenix it'll be extended display mode and therefore as dumb as the 130. If I were going to choose I'd go with the 130 as an extended display as the screen is much clearer than the 520.
Finally, and the most recommended of all, would be record on the Edge. If you want optical HR you can broadcast this from the Fenix to the Edge. When you save on the Edge, the activity will sync down to your Fenix and give you the correct recovery stats as if you'd done it on the watch. This is called True up and is a recently added feature so you'll need to be up to date on firmwares. Hope that helps :)

Hello.
I have similar situation. Had Fenix 5 and just bought Edge 130. Still didn't try extended display. On the Edge 130 side - Fenix 5 has more Firstbit stuff, like training status, etc. So it would be lost in case of recording an activity with Edge. Am I right?