I think there are two questions here:
"Which pen kit(s) and blanks do you like to hold in your hand for writing?"
"Which pen refills do you like for their writing qualities?"
You could also ask a third question:
"How do you like to shape your pens for personal use when you turn them? Straight? Curved? Something more elaborate?"
For my own personal use, I like medium size pen and pencil sets. For feel in the hand, I prefer to turn my own pens as straight cylinders. My friends tease me about the plainness of the shaping, but that's how I like them to feel in my hand for writing.
I keep a Slimline Pro pen and pencil set (Gold) in Kryptonite Glow Stonez at my desk. I bought the pen kit at Rockler and ordered the matching pencil kit from Penn State. The pen kit came with a gel refill, and I refill it with a Parker Quink Gel medium black refill. I like the way that gel pens flow onto the paper for writing handwritten letters, notes, and greeting cards.
I also keep extra pens for guests, filling out forms, etc.: A Duraclick EDC (Brass) in a windfall downed Brazilian pepper tree branch, and a Gatsby twist (Gold Titanium Nitride) in Holographic Black (inlace acrylester). Both have whatever ballpoint refills they came with, or replaced with Schmidt EasyFlow 9000 medium (for myself) when they run out.
In the shop I have Rockler Long Wood pen and pencil set in zebrawood. I use that pencil and its 0.7 mm HB lead for most of my shop work. I also have 0.5 and 0.3 drafting pencils and a marking knife for when I need very fine lines. Sometimes the purpose of the pencil is to help me see the marking knife lines.
Links:
Pen and Pencil Set at Desk:
https://www.rockler.com/slimline-pro-gel-click-pen-hardware-kit-24k-gold
https://www.pennstateind.com/store/PK-PCLXX.html
https://www.rockler.com/kryptonite-glow-stonez-pen-blank
"Guest" Pens at Desk:
https://www.pennstateind.com/store/PKEDCDBR.html
(See photo of test blank and resulting pen from Brazilian pepper tree, below.)
https://www.rockler.com/gatsby-twist-pen-hardware-kit-gold-titanium-nitride
https://www.rockler.com/inlace-acrylester-pen-blank-holographic-black
Pen and Pencil Set in Shop:
https://www.rockler.com/long-wood-click-pen-hardware-kit-gold
https://www.rockler.com/longwood-click-pencil-hardware-kit
(Zebrawood pen blanks cut from the end of a zebrawood board.)
Refills:
https://www.parkerpen.com/inks-refills/ballpoint-pen-refills/parker-gel-2-refills/SAP_2136231.html
https://www.schmidttechnology.com/en/schreibgeraete/produkte/easyflow/c_1_9.htm
Photos:
- Office Desk: Slimline Pro pen and pencil set in Kryptonite Glow Stonez.
- Office Desk: Duraclick EDC pen in Brazilian pepper, with original test turning from the same downed branch. The turned pen did not live up to the artistic promise of the test blank, but the pen is very comfortable in the hand.
- Office Desk: Gatsby twist pen in Holographic Black (inlace acrylester).
- Shop: Long Wood (or Longwood) pen and pencil set in zebrawood.
