DxO PhotoLab achieves the same results in terms of noise reduction and subtle sharpening, has a much more attractive interface and is much faster to process images than any Topaz software. Still PhotoLab has the same issues with roundtripping as the other plugins though. Affinity Photo should really fix its plugin issues once and for all. Weak plugin support is one of the biggest differentiators from Photoshop. Photoshop has ACR for RAW import which is head and shoulders above Affinity Photo's RAW processing. All the more reason for Affinity Photo to play well with other applications and plugins.
In terms of colour, if a photographer wants to use a collaborative workflow between applications and plugins, s/he's really best served by restricting him or herself to sRGB. Yes, there's some missing colour range (not visible on most monitors or even most printers' works) but at least the colours are consistent.
Great workaround. Thanks for that.