I have experienced both these “phases/stages”, and they are distinctively different from each other.
One of the most unforgettable difference is the the fact that if you are in Surrender, you can not experience Separation
For me, Surrender helped to crash my doubts, my fears, my insecurities. I had to choose to let go of these illusions that I had about myself, my life and my perspective of life.
I chose to let go of neediness to control my Twin Flame Process. I gave up my expectations, and instead I focused on learning from being a Twin Flame.
I had to let go of my old self to accept to fully embody Twin Flame Love and Energy.
I realized that I had to give up one for the other. This was so difficult because I had to accept change. Change from my old life to the now Authentic person that I am.
I had to trust the New Experience, the new feelings, new change, and the unconditional love in my heart.
Separation on the other hand, was a negative experience for me. I had to learn the toughest lessons to understand that Twin Flames are never separated.
Separation for Twin Flames is an illusion.
You are one Soul as Twin Flames but it takes a series of Soul lessons to understand this fact.
Physical separation happens for everyone, Twin Flames are not an exception but the difference is that during physical separation, it is when I could feel all the love in my Twin Flame Connection.
For sure absence makes the heart to grow fonder.
Physical Separation has taught me so many love lessons, especially self-love. Love begins from within you.
Physical separation exists to teach you that Twin Flame Love is inseparable, you can not split a Soul. You can not separate Love.
I hope this helps. Blessings
I wish you the best of Luck and Blessings on your Journey.
Stay in Love!