My biggest regret in my current tank is starting with one of the magnet scrapers that has the scouring pad. I put two nice scratches in the glass and then switched to Tunze. Should’ve started with Tunze from the outset.
My glass is 1/2” and what I found works really well is I bought two - one regular and one strong. I swapped the dry sides so now each set has a regular and a strong magnet. I keep one with plastic blades and one with metal. The plastic is my go to 90% of the time and I use the metal occasionally for stubborn spots and because it reaches into corners a bit better.
With the plastic blade I think the risk of a scratch is close to zero. The metal is pretty safe too (on glass) but seems like a slightly higher risk than the plastic.