Comment 55 for bug 1087519

What you see in grub DEAFAULT command line at boot time is taken from GRUB_CMDLINE_LINUX_DEFAULT
What you see at another grub menu item's command line (e.g recovery mode, or another kernel version) is taken from GRUB_CMDLINE_LINUX.

What is there more is "pure linux meet", it is kernel image name, root directory and initramfs specification.

Splash means you want see a picture not text while booting.
When booting printk utility prints a lot of messages to console. To avoid this noise most people use "quiet" kernel option.
All the avoided messages may be seen later in /var/log/dmesg.
It is up to you what you want to see on console at boot time. It will not however change any system funcionality.

Upon BIOS upgrade my modem is dumb again.

Many people complain about wrong IRQ care on modern mobos with 3.x.x kernels. It does not relate to modem cards only. However it is specific to PCI bus I think. PCI-E has different IRQ handling than PCI. There is a bus messaging, not PIRQ signalling.

I think I will wait for right solution.

Another more bad experience titled "Never buy new hardware for Linux".