I'm currently have a few tables with InnoDB Engine. 10-20 connections are constantly inserts data into those tables. I use MySQL RDS instance on AWS. Metric shows about 300 Write IOPS (counts/second). However, INSERT operations lock the table, and if someone want to perform a query like SELECT COUNT(*) FROM table; it could literally take a few hours for the first time before MySQL cache the result.
I'm not a DBA and my knowledge about DB are very limited. So the question is if I'll switch to MyISAM Engine will it help to improve the time of READ operations?
SELECT COUNT(*) without WHERE is bad query for InnoDB, as it does not cache the row count like MyISAM do. So if you have issue with this particular query, you have to cache the count somewhere - in a stats table for example.
After you remove this specific type of query, you can talk about InnoDB vs MyISAM read performance. Generally writes do not block reads in InnoDB - is uses MVCC for this. InnoDB performance however is very dependent of how much RAM you have set for the buffer pool.
InnoDB and MyISAM are very different in how they store data. You can always optimize for one of them and knowing the differences can help you in designing your application. Generally you can have as good performance for reading as in MyISAM in InnoDB tables - you just can use count without where clause, and you always should have a suitable index for where clauses, as in InnoDB table scan will be slower than in MyISAM.