The purpose of Back EMF is to ensure the loco runs at a constant speed at a given speed step, regardless of load (assuming that's within the engine's capability in the first place!) and, more importantly, when encountering gradients. If you have partially disabled Back EMF, which is what you are doing by setting a value in CV 10, then trains may slow down when going uphill and accelerate downhill. That might be OK if you are driving the engine directly and can adjust the throttle, but not if you are leaving the train to run whilst doing something else. In addition, using any form of automation, such as RR&Co, will make this issue more obvious.
You should only have to adjust CVs to match the performance of the loco in question, not to overcome a deficiency in the decoder itself. With TCS decoders, I found that with some engines, the maximum speed was achieved at speed step 26. For example a Hornby West Country was measured by RR&Co at 81 mph on step 28 but 87 mph on step 26, which of course resulted in erratic running even when being driven manually. The lurch is characteristic of both the TCS and DCC Concepts decoders I once used.
As already mentioned, you get what you pay for and having spent £100+ on a fine loco it seems to me false economy to install a cheap decoder with a known shortcoming, when better decoders are available for not much more money. The Lenz Standard+ is an excellent decoder, and available from about £16 (DC Kits, Model Railways Direct) and £18 from Hatton's. Unlike DCC Concepts and TCS decoders, Lenz ones also have the benefit of short circuit protection which eliminates the risk of the decoder burning out if you short circuit it.