Mean Group Estimation applicable for short (3 N, 30 T) and long (120 N, 30 T) panel?

[Muhammad Ibrahim Shah]

Can panel data techniques such as Mean group (MG), Augmented mean group (AMG) and Common correlated effect mean group (CCEMG) be applied for small groups of countries such as only 3 and with 30 years of data for each? What about a long panel where N>T (say 120 countries and 30 years), in that case, can we apply these three?