Cloudflare is a WAF/Proxy that can handle DDoS, it isn't a DDoS specific product. If your actual network space is getting hit (e.g. 8.8.8.8) cloudflare will not help you.
Depends on the type of DDoS. Traffic may saturate your internet connection regardless of there being a firewall on your end. In which case you need a provider capable of handling the full bandwidth of the DDoS sitting in front of you.