Almost all organic solvents will cause injection-moulded plastics to swell up, soften and dissolve in the liquid, gel, cream or paste that they are presented in to the customer. Acetone (usually the solvent in cheap nail varnish) is increasingly being added to acrylic paints to enable them to key into the plastic kits and it is considered less dangerous to the public in spray paints that used to contain toluene and benzene but it can be absorbed through the skin and it will dissolve the cornea if you get any in your eyes. Methylated spirits is ethyl alcohol with 5-10% of methyl alcohol (methanol) to make it highly poisonous if you drink it at all but methanol can be absorbed through the skin, so wear rubber gloves. The purple stuff has dye and pyridine added to give it a minging smell but you do not want me to tell you what that will do to you when it gets inside your body. Use tongs to hold wet models.
So, do not use organic compounds (the ones with strong smells) as strippers on plastic models.
If you do use these chemicals for paint stripping on metal, use rubber gloves and wear a face mask and eye protection and clear up your working area with soapy water afterwards.
Modelstrip paste and its industrial-quantity big brother, Ronstrip, is a paste containing sodium hydroxide (caustic soda), so all precautions to be followed for the latter should be followed for the pastes. They dissolve skin, hair and glass, so use a polythene or polypropylene container (a 2 litre icecream container will hold most mini-ships) and wear all the protection above and use nylon brushes to agitate the surface of the plastic, not sable or squirrel hair brushes. You will need the face mask because when you add the solid stripper to water, if you live in a hard water area, it will liberate carbon dioxide from the water and the bubbles will be breathed in and attack the skin in your nose, throat and lungs....
Do not use sodium hydroxide on metals. Some will dissolve (Aluminium, magnesium, zinc and MAZAK and some will oxidise and go black, so use an organic stripper for metals.
To summarise: All paint strippers are dangerous. However, you should remember that in general, chemists have a higher than average life expectancy because they know what they are working with and, secondly, remember that the most ubiquitous chemical, water, is dangerous in large enough quantities!