Best update strategy with MyISAM

[mos]

I will have an application that will have 1000 20 row selects executed 
every second. The application will also be updating individual rows from 
this table at a rate of 100 rows/second. I prefer to use MyISAM instead of 
InnoDb because eventually the table will exceed the amount of memory on the 
machine and InnoDb is too slow if the table doesn't fit into memory.

With MyISAM:
1) Will the updates block the Select statements from executing? If so, is 
there a way around it? I don't want to stop the Select's from executing by 
having them wait for an update lock to complete.
2) Is it better to update a secondary table and then use a Select with a 
join to display the results? Or will it matter?

TIA

Mike