I use my Mk1 Golf Gti cabriolet (same engine as yours) as my daily drive and have for over 20 years. The original engine lasted 27 years and 270,000 miles before it started to use a lot of oil, 500 miles for 1/2l oil and I could leave a good smoke screen when I floored it
I found a replacement DX engine with 100,000 miles took the head off just to check it over as it was sat outside in a garden for 4 years and it was all good inside, the replacement engine as a good engine, does not burn any oil, plenty quick enough as I do sometimes drive it like I stole it and easily keeps up with most modern cars, I even surprise some BMW drivers... it returns a good 40 mpg on a steady drive to work (50 mile commute to and from work), it’s an easy engine to work on and most parts are cheap and easy to get hold of.
My Golfs now on 295,000 miles and there is a Mk2 Scirocco on here with 500,000 miles on the clock so plenty of life in your engine.
10,000 mile or 12 month 10w40 semi synthetic oil and good quality MANN or genuine VW oil filter changes.
20,000 mile or 2 years for fuel filter.
Buy a K&N panel air filter so you only have to clean it every 50,000 miles and don’t ever need to buy another air filter.
Change gearbox oil every 40,000 miles or 4 years with fully synthetic oil.
20,000 miles or 2 years for spark plugs, HT leads, dissy cap and rotor arm.
Check which type/colour of coolant is in the car and if needed change that on regular basis.
Cambelt and tensioner every 40,000 miles or 4 years.
Fuel injectors last about 100,000 miles so if start up when cold is lumpy and ok when warm it’s usally leaking fuel injectors..
You will have a very reliable engine which should see you for another 100,000 miles no problem.
Keep a close eye on the fuel filler neck and clean the mud from around the filler neck underneath the wheel arch and any signs of rust appearing inside the pipe when filling up change the filler neck as water, dirt etc in the tank will kill the fuel injection system, it starts to get expensive replacing bits of that...