Dental cavities: Root canal and dental filling questions...

Off late I have been facing some dental problems. Recently, one dentist told me the following:

- 4 of my teeth have cavities
- out of these 1 requires root canal

I am taking second opinion and then would move ahead with the appropriate treatment. Would prefer a biological dentist.

My questions:
- Is filling these cavities by composite filing the best way, or should some other process be done?
- Since root canal is not preferred, in such cases what could be the alternative? My teeth start hurting and the usual pain to the nerve connecting to the brain starts as soon as I eat something.

Any other suggestion I must consider while going for the treatment would be helpful.

I never had any amalgam filling done, earlier ones were composite fillings that came out.

I am not covered by any dental insurance plan, so would need to bear the entire cost. I am going through treatment for parasites for the last 2-3 years.

Not much aware about the dental treatment, therefore some questions might have been too basic, thank you for the patience and help.