@Hops I'm glad you found this post helpful and I'll continue to follow up with my experience with the bike.
In terms of touring, I don't think I have the experience necessary to give you any really solid feedback as I my rides are typically single day loops and out and backs. That said, I can say this about the Synapse Neo...
- It's very comfortable to ride 100+ km. As always, assuming you have a good fit and the saddle that works best for you.
- it's versatile with the option to swap out your wheels (700c / 650b). I'm loving the 650b wheels combined with the WTB Byway tires (47 mm). Frankly, I can't recommend the Byway tires enough. They're quick on the asphalt and grippy and comfortable on the gravel.
- Once you've sorted out a battery swapping system (perhaps another post I might make based on my experience) it's very easy to switch out the battery while out on a longer ride (100+ km). My system/method allows me to swap out the battery in a couple of minutes (e.g. while on a water stop). I ride the XL and can easily carry the second battery in a half frame bag. Also, I don't find that the added carrying weight of the second battery is significantly impacting the range I'm getting on a single battery. I'll carry the second battery on rides more than 70 km, just in case I hit some super hilly routes or very strong headwinds.
- The bike does include mounting points for a back rack although I haven't set it up for this yet. It's on the list for sure. If you plan to ride with a rack and frame bags there are lots of available options. I went with a pricey Goldback bag (saddle bag/handlebar - Bags by Bird) and love it. I use it as a handlebar bag. I use the Topeak Midloader (4.5 L) to carry the second battery and some tools. I also recently added two feed bags for the handlebars (Chrome Doubletrack). While bag systems work well and you can mount a rear rack, there aren't a lot of mounting points (i.e. eyelets) when compared to a proper touring bike. That may or may not be an issue for some.
I'll be using the Synapse Neo for some bike packing/touring trips that are typically asphalt and gravel road/trail routes. It's important to note that I haven't actually done this yet. I won't be doing much in the way of single track or heavy gravel routes. To address your question, I think you could make the bike work well for touring. While it lacks a full touring layout, the Synapse Neo does have a rack mounting option and with today's bike bag systems, I think you'll be able to spec it out according to your needs. Simply put, I would be comfortable using the bike for touring based on how I ride and where I ride. Hope that helps to provide some additional insight.