Are they safe? I'm nit sure if they are lead or not or if they are harmful for the fish

I use Penn Plax Anchors all the time for plants. No ill effects on anything that I've seen.

AFAIK they are all zinc.

Lead is superior in both weight and flexibility. So in the US, unless it specifically says lead-free, it's probably lead.

Some other countries have banned lead weights, more for disposal concerns that for the health of fish; and use zinc exclusively.

I wouldn't worry about the effects of lead in the aquarium. But with a little practice, you'll generally find weights unnecessary to successfully anchor plants.

Zip ties and rocks...

I use "safety-flo" solder. You can find it in the plumbing section of a hardware store. I use it in my tank and have not run into any issues. The stuff is really cheap and rated for potable water. It's a bit stiff & shiny, but the price, convenience, and availability is hard to beat.

I make little stakes out of paperclips.

I've used leaded plant weights for years to sink pieces of zucchini and spinach for shrimp and have never once had a problem.