Keep Things 3 as is and just add Noti on top.
Your original is untouched. 3 steps, done in minutes.
Migration steps
1
Export from Things
In Things, export projects and to-dos as text, or copy them.
2
Area/Project = lists
Reconstruct Things Areas and Projects as Noti lists.
3
Import into Noti
Deadlines become to-do due dates and notes come in as notes. Date expressions become event candidates.
Sync. Things is Apple-only. Noti is a PWA, so you can see the same to-dos on Android and PC.
Frequently asked questions
Can I use it on Android?
Yes. Noti is a PWA, so you use the same data anywhere — Android, PC, or iPhone.
Are there views like Today/Upcoming?
You can build something similar with the today and upcoming screens plus list filters.