Always double check for color conversion "problems". This always happens.
I.e. check yellows for blue contamination/check greens for magenta contamination etc....
Go over the image with a fine toothed eye dropper
Other than that, it's a great cmyk system.
What are your CMYK dot gain (curves)/black generation/ink limit settings?
Well, there ya go. That's the difference between conversion and loading color presets.
It's one thing to load a color set that matches the inks. That's one of the good things to do.
There is more, (when you convert the RGB - to a CMYK color setting), what does that do?
It gets pretty congested with options (and for various art). You may not want to use one RGB to CMYK conversion for dark muted colors and you may choose another setup for a very bright design with near rich (heavy %'s of straight up Cyan, Magenta etc. It's all different.
Some people can get by (at random times) getting a fantastic result this time...not knowing why they did so well ....and other times they do a CMYK with the same settings to find that it's just not working. The color settings should be tweaked before each conversion.
To boot, you then will need to adjust manually in the channels. That can be by isolating an area with a selection and cutting it back or adding to...or it could just be by taking the 50% area and dropping it down to 40% (in each channel). I do both for most people.
I first use the conversion of my many options. I think I have about 12. Then, I review the seps, consider the mesh, consider the garment color (often white), but sometimes its light colors with a base. All of these make a difference.
For the most part, you can do pretty good with just always using UCR (Under Color Removal) but sometimes, I use GCR (Gray Component Replacement).
In general, the total ink should be about 260-270
Black ink limit should be 100.
Black generation will be in various options of MAX, Heavy, Medium and Light.
This determines really, (how much) color content is in each channel to make up the same art.
Offset printers will use something totally different than we do.