Re: Utilize maximum system resources for better performance

[Rick James]

Memory allocation: http://mysql.rjweb.org/doc.php/memory

For MyISAM, _Most_ of the RAM should be left for caching the _data_ of MyISAM tables. So, 29GB/32GB free is about right.
key_buffer_size is about half what it should be.

> KEY `e_v` (`enabled`,`verified`),
> KEY `e` (`enabled`),

The latter index is redundant with the former, and can be DROPped.

> `hash` char(40) COLLATE utf8_unicode_ci NOT NULL DEFAULT '',

Is the "hash" a hex string? UUID? You are currently allocating 120 bytes (per row) for `hash`.
For an MD5, CHAR(32) CHARACTER SET ascii -- 32 bytes
For a UUID, CHAR(36) CHARACTER SET ascii -- 36 bytes

> ROW_FORMAT=FIXED

Don't use that; it's an old wives tale that there is any benefit from it.

> WHERE enabled = 1 ORDER BY upload_date DESC

would benefit from INDEX(enabled, upload_date)

> LIMIT 6514850,25

Get real! Under what condition do you need to jump to row number 6514850?? The query _must_ scan 6514850 rows before finding the 25 you want.

> log_queries_not_using_indexes = 1

That clutters the slowlog, without providing useful info.

> will switching to innodb improve overall read performance ?

Not for _this_ query. But InnoDB is better in general.