Will this work with win xp sp3 ?

I'm not sure, but I don't see why not, considering it's using SMB. I've only used it with Win 10, Macs, and Linux.

What is the power converter specs. Is the output 12v?

AC Input: 100-240V-1.0A 50-70 Hz DC Output: 12V-3A

Can I use this to sync to google? & if so, can you choose to reduce photos to high res, instead of full size photos?

Synology will sync files to or from Google Drive, but it can't do anything at all with Google Photos (which is a separate service), and it can't resize or modify anything.

Synology 1 bay NAS DiskStation DS118 (Diskless)

DiskStation® DS118

High-performance 1-bay NAS for small office and home users

Versatile, powerful and compact storage server

Synology DS118 comes with a new 64-bit quad-core processor, delivering excellent data transfer speed and 10-bit 4K H.265 video transcoding on the fly.

CPU

Quad-core 1.4 GHz

Memory

1GB DDR4

Performance

Over 113 MB/s and 112 MB/s sequential reading and writing

Eco-friendly

9.4 W / 4.22 W Access / Hibernation power consumption

Ultimate file management and sharing

File Station is a web-based, fast and secure management tool built to allow easy, drag-and-drop operations without requiring any complex setup on Mac or PC. Advanced search and filtering tools allow for easy organization and file sharing. For complete compatibility, DS118 supports the following protocols: AFP, FTP, iSCSI, NFS, SMB, and WebDAV.

Easy file access with QuickConnect

Access files on your Synology NAS over the Internet without the hassle of setting up port forwarding rules, DDNS, or other complicated network settings. QuickConnect allows you to connect via a secure, customizable address, so that you can instantly access media and work files on any Internet-connected device with no additional charge.

Stream content to your TV

Turn your Synology NAS into a home media hub and stream your digital contents to computers, mobile devices, Samsung TV, Apple TV, Google Chromecast, and DLNA devices.

Access and sync your files seamlessly

Synology Drive provides a built-in universal portal to access your data anytime and anywhere, and synchronize all your files across platforms, including Windows, macOS, Linux, Android, and iOS.

Sync files on demand: Save the storage space and network bandwidth of your PC.
Go back in time: Easily retrieve previous versions of your shared files.
Back up your data: Protect your files as scheduled or in real-time.

Powered by Synology DiskStation Manager

Surveillance Station

Complete surveillance solution for recording, monitoring, and management.

Desktop Backup

Simplified backup solution for your Mac, PC, and mobile devices.

Public Cloud Integration

Back up and synchronize data easily between public cloud accounts and your NAS.

DSM UI

Award-winning operating system with an intuitive user interface and powerful capabilities.

Security

Secure data with comprehensive built-in security tools to protect your devices against evolving threats.