Naaa…
don’t consider this, we are talking about more performance aren’t we?..
Single channel in 2018/19?
For my digital experience in the last few decades I strongly would prefer to have better performance over more ram. So, of course have dual-channel.
I consider 4GB ram for such a device as totally sufficient. I somehow cannot understand the reasons for some users wanting to have more than 4GB ram in such a device. What are they doing with it? Reaching out for mobile virtualization?? 
I mean having a computer replacement is one thing, but staying realistic is another. We are talking about a (mid-range) smartphone, not the latest top-notch on the market. Please stay a bit more down to earth. FP is not yet far enough to approach Apple, Samsung or other big boys heights. Three iterations are simply too less for this goal.
I think many users wanting to have 8GB in their handset probably don’t even keep a standard notebook with more than 4GB physical ram. So what’s the deal?
And still this is a Linux based OS not Windows. Yes, Windows may be run on this hardware, but if that’s the goal I am afraid there need to be two hardware options depending on the OS the user prefers to run.
I prefer to stick to (any) kind of Linux based OS, it’s unlikely that I want to pay for a 8GB ram unit knowing that it may take years to come needing that much ram, hence having to pay a noticeable higher amount for more (just in case/nice to have) ram I would not like and probably would decide against a purchase of such an oversized unit.
Actually I am following the launch of the (new) AMD Ryzen mobile APUs e.g.
5 2500/2600 & 7 2700/2800.
There are new notebooks out there (Acer/Lenovo) with a single channel ram design but keeping the stronger APU 7 line next to the the weaker APU 5 line with dual channel design which after all outperforms the stronger APU due to this imo design flaw just for the sake of low-costs. I´m helping to save costs and won’t purchase one such unit. 
Which one you would go for if having to take a decision and also in price comparison? (this one should be easy…).
There are FP2 users out there complaining about a lack of performance. Some complain about regularly running low on ram e.g. while browsing.
Both could be helped with 4GB ram as dual-channel setup.
Considering that all is working in form of more or less large memory shifts, it’s even more vital to have better performance (bandwidth) the more memory is available. I think performance is always the center key to focus on as it directly takes influence in the user experience.