I have a Roland space echo RE201 pedal and an eventide space. I use them on my analog synths.
I used to use the roland space echo 201 on my moog voyager although now I use the eventide space. I have an oberhiem obx8 although I don’t use any effects on it. It has a great sonic character in and of itself. The seq pro 3 has internal effects. I have a Yamaha AN1X that has internal effects also.
A lot of romplers have internal effects as well. I never used external effects on my romplers.
Using effects on my voyager made a big difference. Reverb and delay work well on monophonic synths. I have my voyager midied to my Korg Arp Odyssey. I don’t use effects on the Odyssey just the voyager. I simply adjust the ADSR on the odyssey so it decays in time with the voyager maybe I should try effects with my romplers , maybe it will a difference. I find that you have to use taste
In the amount of effects you use otherwise it can ruin the character and sound of the synth. It’s a balancing act. The oberhiem obX8 is a synth that sounds great utilizing its stereo pan and has so much presence that it sounds like it has effects on it even though it doesn’t. I think that’s one of its strengths. That synth breathes and sounds alive sonically even without effects.