I attach the strand to a closed jump ring. I attach clasps with sturdy open
oval jump rings. The opening is on the side of the oval, so less chance of the strand pulling through. If the gauge on the jump ring is big enough, it will be strong enough for most designs. And it allows for a clasp change.
You could use a closed jump ring on both ends, for that matter, then use open jump rings on both ends--that would let you switch out even to a toggle clasp, using oval jump rings to attach new findings at both ends...
I quit using split rings because they rotate and the rough ends always caught in my hair or clothing. I don't know if they're hideous or unprofessional, but I have to admit, I just don't like the way they look anymore.

If customers want a different clasp and I've made the necklace so it can't be easily switched, I make it very easy for them to put in a special order for the same design with different clasp, with free shipping if that's what it takes to get them to commit.
And I know it sounds boring, but I try to keep my clasp/closure options to a minimum. I've learned you can't please everyone, and trying to have "something for everyone" drove me nuts. It's better for me to keep the creativity in the design itself and streamline my closure process. (Well THAT sentence sounded odd....)